This method comprises: conveying in the conveyance direction a composite sheet that is formed by inserting an elastic member between a thermoplastic first continuous sheet and a thermoplastic second continuous sheet and fixing the elastic member with a thermoplastic adhesive and forming in the composite sheet a high stretchability region and a low stretchability region in a row in the conveyance direction by cutting the elastic member at one or more locations in the conveyance direction in a region corresponding to the low stretchability region. During such forming after a heating member heats at least one of a cutter rotary body and an anvil rotary body which rotate such that the respective outer peripheral surfaces thereof are mutually opposed so that the temperature of said at least one rotary body remains lower than the melting point of the adhesive the anvil rotary body and a cutter blade on the outer peripheral surface of the cutter rotary body compressively clamp the composite sheet when the composite sheet passes between the cutter rotary body and the anvil rotary body along the conveyance direction such that a crimped part between the first continuous sheet and the second continuous sheet is formed at the position where the composite sheet is compressively clamped while the elastic member is cut.
