To provide a method of joining metallic sheets in which work such as welding and binding is unnecessary, positional shift is not caused between both metallic sheets and by which rigid joining strength is obtained when two metallic sheets are joined together.

This method includes: a step where a bent piece 1b is formed by bending the end part of a first metallic sheet 1 which is a metallic sheet on one side of the two metallic sheets into an acute angle with respect to the base portion 1a of the first metallic sheet; a step where a bent piece 2b is formed so that an opening 1d which is shorter than the maximum distance between the bent piece 1b of the first metallic sheet 1 and the base part 1a is opened to this base portion 2a of the second metallic sheet 2 by bending the end part of the second metallic sheet 2 which is the other metallic sheet of the two metallic sheets; and a step where the first and second metallic sheets 1, 2 are joined together by utilizing the springback of this bent piece 1b of the first metallic sheet 1 by making the bent piece 1b of the first metallic sheet 1 and a base portion 1b opposing to that enter between the bent piece 2b of the second metallic sheet 2a and the base portion 2a opposing to that from the opening 1d and bending the bent piece 1b of the first metallic sheet 1 to a more acute angle.