PURPOSE: To reduce the number of parts for a cassette by engaging with the spring of a stapler main body at the cassette fitting time on to a stapler and providing a knob for transferring the staple contained in the cassette to a striking out hole on a feeding piece.

CONSTITUTION: When a cassette is fitted to a stapler, the knob 7 provided at the head part of a feeding piece 3 is engaged with the engaging part of a spring tip provided on the handle of a stapler main body 1. By this engagement, the feeding piece 3 is moved in the tip direction of the cassette to delay or press the staple 2 of the inside of the cassette so as to transfer to a striking out hole 5.