An air-bag module mounting structure where a fixing part 88 of a hub 80 of a steering wheel is fastened to a fastened part 24 of a horn plate 20 to which an air-bag module is fixed. A body cover 30 includes a positioning pin 31 protruding toward the hub 80 and a hook 38 protruding from a side surface 37 of the positioning pin 31. The hub 80 includes an insertion hole 84 into which the positioning pin 31 is inserted and with which the hook 38 engages; and a stopper 87 that prevents the horn plate 20 from moving, because of a gap d2 existing between the insertion hole 84 and the positioning pin 31, when the fixing part 88 and the fastened part 24 are fastened together. The gap d2 allows the positioning pin 31 to pass through the insertion hole 84 while the positioning pin 31 is bent due to a contact between the hook 38 and the insertion hole 84.