PURPOSE: To contrive the improvement of productivity and the conservation of an undercoating agent while inhibiting rifts in a coating film, by contracting the method of coating a can body into the application of an undercoating agent onto an inner surface → drying → the application of an undercoating agent onto an outer surface → the application of white paint → drying, in sequence.

CONSTITUTION: An inner undercoat layer 2 is formed all over the inner surface of a can body material 1 and dried. Thereafter, an undercoating agent is applied onto the bonded part of its outer surface. Without drying said undercoating agent, white paint is applied in a state slightly overlapping the end part of the undercoat layer 3. The undercoat layer 3 and the white paint layer 5 are then dried in an oven at the same time. Thus, rust to be formed at rifts in the coating film, exfoliation, etc. are inhibited by the contracted process, while improving productivity and curtailing the undercoating agent.