She did not win a singles title on WTA Tour in her career, however did reach one final in Tashkent in 2003 where she lost in two sets to Virginia Ruano Pascual.

Having had moderate success on the ITF Junior Circuit – reaching a career high ranking of 55 – Obata made her WTA Tour-level professional debut in 1996, at the age of 18, at the Tier IV event at Surabaya, where she lost to Hila Rosen in qualifying, in straight sets.

Her first full season of regular tour-level tennis started at the Tier V tournament in Hobart, where she qualified for the main draw, before losing to Anna Smashnova in two close sets.

Obata then had a breakthrough tournament in the highest-tier Pan Pacific Open in Tokyo, winning through qualifying by beating top seed Kristie Boogert, wildcard Kumiko Iijima and Janette Husárová.

She struggled in the next three tournaments, losing in the first round in Acapulco, Indian Wells and Key Biscayne, before dropping back down to ITF-level at the $25k event in Stone Mountain.

In Japan's Fed Cup tie against Argentina, Obata played two singles matches – losing in straight sets to María Emilia Salerni, before beating Clarisa Fernández by retirement.

In Gifu, she beat Christina Wheeler, compatriot Akiko Morigami and Annabel Ellwood before losing to second seed Alicia Molik in three sets in the semifinals.

At Wimbledon, she again reached the final round of qualifying by beating two British wildcards, Alice Barnes and Helen Crook, before again losing in straight sets to Daniilidou.

A further second-round loss in Pattaya saw Obata decide to finish the season at challenger level with two $25k tournaments in Port Pirie and Nuriootpa, South Australia.

As the top seed, she won the tournament in Port Pirie, beating Yuliya Beygelzimer, Amanda Grahame, Christina Wheeler, Jaslyn Hewitt and Pavlina Nola.

Obata started the year with a warm-up tournament in Australia in Canberra, where she qualified for the main draw, defeating Miho Saeki, Maureen Drake and Lucie Ahl, before falling in the opening round to Anna Smashnova, 1–6, 3–6.

She then qualified for the Tier I Pan Pacific Open in Tokyo, beating Jill Craybas, Jennifer Hopkins and Alicia Molik to reach the main draw.

The grass-court season started badly for Obata, with first-round losses in the Surbiton challenger to Tara Snyder, and in the first round in Birmingham to Dája Bedáňová.

She finished her year with two straight sets, first-round losses at the Japan Open to Jelena Kostanić Tošić and in Pattaya to Adriana Serra Zanetti.

Obata started the year with by qualifying for the Tier V WTA event in Canberra, defeating Claudine Schaul, top seed Dally Randriantefy and Tatiana Poutchek to reach the main draw.

Obata then reached the quarterfinals of the Memphis Tier III tournament, defeating Canadian Vanessa Webb and fourth seed Alexandra Stevenson, before losing to Cho Yoon-jeong.

won the $50k tournament in Fukuoka on carpet, defeating Seiko Okamoto, Nana Miyagi, Jarmila Gajdošová, Zi Yan and then Maria Elena Camerin in the final.

At the Tier I tournament in Toronto, Obata qualified and defeated compatriot Shinobu Asagoe in the first round, before falling to seventh seed Amanda Coetzer.

She reached the semifinals of the Tier III tournament in Bali, defeating Ashley Harkleroad, Barbara Schett and Angelique Widjaja, before finally falling to Chanda Rubin in straight sets.

She ended her season at the Tier V tournament in Pattaya, winning two rounds before falling to Slovakian Ľubomíra Kurhajcová, ensuring her highest-ever year-end ranking of 49.

She retired from her Fed Cup singles match against Dessislava Topalova of Bulgaria, then lost in first rounds at the remaining nine tournaments she played, including her first and only appearance representing Japan in the Olympics, where she was shocked by Maja Matevžič, who had been plagued by an elbow injury for most of the previous year.

Obata finally ended her losing run with a win over wild card Miho Saeki at the Pan Pacific Open in Tokyo, earning a second round meeting with top seed Lindsay Davenport, where she put in a creditable performance in a 3–6, 4–6 loss.

Despite her relatively poor results and subdued ranking, Obata hit a rich vein of form in two challenger in events in Augusta, Georgia, and Gifu.

In the first four rounds, she didn't drop a set – defeating Casey Dellacqua 6–1, 6–1, then New Zealand qualifier Marina Erakovic 6–2, 6–4, before winning against fellow Japanese player Ayumi Morita 6–0, 6–4.

Going on to grass, Saori lost a tight opening round at the $25k event in Surbiton to South African qualifier Surina De Beer, losing in three sets.

At Wimbledon, Obata beat Hana Šromová, Jessica Kirkland and Eva Birnerová to reach the main draw, before losing to American Marissa Irvin in round one.

With a ranking still too low to reach the main draw of the US Open, Obata went into the North American hard court swing needing wins to make it into the top 100.

At the Tier I event at San Diego, she beat Varvara Lepchenko and Alexandra Stevenson to reach the main draw but lost a tough three-set match to Gisela Dulko in the opening round.

Obata's ranking was enough to give her entry to the main draw of the Australian Open, and she started her year with her regular warm-up tournament in Canberra.

In March, Saori entered the $75k event in Las Vegas where, as sixth seed, she defeated Varvara Lepchenko in the opening round, before a 6–3, 6–2 over Swede Hanna Nooni.