Hiroshi Koizumi
Tsukioka

Setsuko Wakayama
Hidemi

Minoru Chiaki
Kobayashi (as Mindru Chiaki)

Takashi Shimura
Dr. Yamane

Masao Shimizu
Dr. Tadokoro

Seijirô Onda
Commander (as Serjiro Onda)

Sonosuke Sawamura
Shibeki

Yoshio Tsuchiya
Tajima

Mayuri Mokushô
Radio Operator

Minosuke Yamada
Chief of Civil Defense (uncredited)

Ren Yamamoto
Ikeda (uncredited)

Shin Ōtomo
Convict Leader (uncredited)

Senkichi Ōmura
Convict (uncredited)

Haruo Nakajima
Gigantis (uncredited)

Katsumi Tezuka
Angurus (uncredited)

Shōichi Hirose
Convict (uncredited)

Keye Luke
Tsukioka / Policeman (voice) (uncredited)

Marvin Miller
Kobayashi / Dr. Yamane / Narrator (voice) (uncredited)

Paul Frees
Commander / Father / Convict (voice) (uncredited)

George Takei
Ikeda / Osaka SDF Dispatcher (voice) (uncredited)

James Yagi
Osaka SDF Captain (voice) (uncredited)