Tomizawa completed his pharmacology studies at the University of Tokyo in 1947 under the guidance of Morizo Ishidate.

Following that, he worked at the Japanese National Institute of Health, conducting research on DNA replication in bacteriophages.

Returning to the Japanese National Institute of Health in 1960, he assumed leadership of the Chemistry Department in 1961 and conducted courses on bacteriophage biology at Kanazawa University.

[2] Additionally, from 1996 to 2006, he served as the founding editor of the scientific journal Genes to Cells, the official publication of the Japanese Society for Molecular Biology.

Moreover, he donated 150 million yen from his private funds to establish a program benefiting young scientists in life sciences.