Manufacturing method for rectangular can

A method for manufacturing a rectangular can body that has a rectangular tube and a bottom, the method comprising:

• a step of forming an intermediate molded article that has the rectangular tube and the bottom, the rectangular tube including a sidewall having an inner wall surface and an outer wall surface;
• and
• a step of forming steps on a pair of facing inner wall surfaces in the rectangular tube, respectively, or forming steps on all of the inner wall surfaces in the rectangular tube,
• wherein the step of forming steps comprises
• providing a die on an outer wall surface side of the sidewall on which the step is to be formed,
• providing a mandrel for sandwiching the sidewall between the mandrel and the die at a portion on a bottom side with respect to a portion where the step is to be formed in the inner wall surface on which the step is to be formed,
• providing a punch, and
• forming the step by performing a plurality of instances of a pressing operation by with the punch, wherein the pressing operation comprises pressing on a side opposite of the bottom side with respect to the portion where the step is to be formed in the inner wall surface on which the step is to be formed and compressing the sidewall between the punch and the die.