Kobayashi studied the history of Asian art, but soon left his studies and began working in the Japanese production company Shochiku. He had been working there for only eight months, when he was drafted and sent to war. During the war, he was held captive by American forces for a year. In fall of 1946, he came back to Shochiku as director Keisuke Kinoshito’s assistant. Kinoshito wrote the screenplay for Kobayashi’s second film Sincerity (Magokoro, 1953). Afterwards he made The Thick-Walled Room (Kabe atsuki heya, 1953), I'll Buy You (Anata kaimasu, 1956) and The Human Condition (Ningen no joken, 1959.-1961.), war trilogy which brought him international success. His other films include Harakiri (Seppuku, 1962), Ghost Stories (Kwaidan, 1965), his first film in color, Rebellion (Joi-uchi, 1967), At the Risk of My Life (Inochi bonifuro, 1971), Glowing Autumn (Moeru aki, 1979) and The Empty Table (Shokutaku no nai ie, 1985).