A method for manufacturing a pants-type diaper of the present invention includes: a step of carrying a diaper body in a longitudinal direction X; a first folding step of folding a side panel 3 along a first line L1 extending in the longitudinal direction; a first attachment step of attaching first end portions 31 of a pair of side panels 3 to end portions 20a (21a), opposing each other in a girth direction Y, of the front portion 20 or the back portion 21; a second folding step of folding the diaper body 2 along a second line L2 extending along the girth direction Y so that the front portion 20 and the back portion 21 lie on each other; and a second attachment step of attaching second end portions 32 of the pair of side panels 3 to end portions, opposing each other in the girth direction Y, of the back portion 21 or the front portion 20, to which the side panel 3 has not been attached in the first attachment step.