A staple feeding mechanism includes the components of only a magazine 40 with a pair of guides and spring receiver 75 to 77 being integrated, a driving shaft 13 having a double function and a staple feeding member 70 (inclusive of the feeding nail 71 and spring 74) movably arranged in the magazine 40. The feeding nail 71 of the staple feeding member 70 at the home position is lowered by the driving shaft 13 and retracted from the staple cartridge 80. For this reason, the loading/unloading of the staple cartridge 80 can be done without any hitch. The staple feeding mechanism only requires a necessary minimized number of components and so is simple in structure. Thus, the stapler can be provided at low cost. Particularly, the driving shaft 13 necessary to cause the magazine 40 to make a reciprocating motion is also used as a fulcrum member, thus requiring no new component. This further reduces the number of necessary components and also contributes to space saving.