To provide a polishing disk attachment/detachment device for a hand grinder that speedily attaches and detaches a polishing disk, minimizes a shake phenomenon in operation, and places a safety key for preventing a slacking phenomenon of the polishing disk in gentle operation.

The polishing disk attachment/detachment device includes a first grinder body 10 having a driving shaft 11, a coupler 20 divided into a first housing 21A and a second housing 21B, and a binding unit 40 fastened to the driving shaft 11 and having an engagement projection 42a on an upper-end outer peripheral surface. An annular leaf spring 31 which swells upward is mounted to the coupler so as to absorb a shake phenomenon of the polishing disk D, and the first housing 21A is provided with a pair of recessed storage grooves at both side of a flat plate and the safety keys are mounted in the recessed storage grooves, and the second housing 21B has a flange formed downward and includes a guide groove so that the safety key can slide and move horizontally.