Provided are a disposable diaper production method and a disposable diaper production device by which cutting positions of respective side pieces can be accurately managed. A partly-finished product (1Z) is conveyed in a longitudinal direction in a state in which both side portions in the width direction of the cutting position of respective side panel pieces (3 and 4) are held for each set of the two side panel pieces (3 and 4) when the respective side panel pieces (3 and 4) are cut off by a cutting unit (17). A controller (20) controls driving rates of a cutting motor (33) and a conveying motor (39) to rotate driving blades (27) at a rate faster than the conveying rate of the partly-finished product (1Z).
