Masato Seto was born in Udon Thani, Thailand, to a Japanese father and a Vietnamese Thai mother. He moved to Fukushima Prefecture, Japan in 1961, and studied photography at Tōkyō Shashin Senmon Gakkō (東京写真専門学校), graduating in 1973. After further study under Daidō Moriyama, Seto became an assistant to Masahisa Fukase in 1978. In 1981 he became a freelancer.
Seto received the 21st Kimura Ihei Award for Silent Mode (’95) and Living Room, Tokyo (’96), and the Shincho Gakugei Award for his autobiographical essay Tooi to Masato (’99). Other photo collections include Bangkok, Hanoi 1982 -1987 (’90), and binran (‘08), a series of photographs of Taiwanese women selling betel nuts in glass cases with electric spectaculars by the roadside, for which he received the Photographic Society of Japan’s Annual Award.
In addition to being a photographer, his wide-ranging work in the field of photography includes functioning as a judge at the Kimura Ihei Award.