He is a member of the ruling Liberal Democratic Party and a former member of the House of Representatives in the National Diet (national legislature).

A native of Nishinomiya, Hyogo, and an alumnus of the University of Tokyo, he joined the Ministry of Transport in 1977.

During his time out of office, he matriculated as a postgraduate student and studied international law and business at Kobe University, which is located in his constituency.

[2] In 2024, Moriyama won a no-confidence motion issued by the Constitutional Democratic Party after reports emerged that he received a letter of recommendation and campaign support from an organization linked to the Unification Church during the 2021 Japanese general election.

[3] On 10 April 2024, Moriyama was among the guests invited to the state dinner hosted by U.S. President Joe Biden in honor of Prime Minister Fumio Kishida at the White House.