A belt installation tool (406) of the present invention includes a pulley pressing part (407) capable of being pressed toward a side of an outer periphery of a crank pulley (2) by the tension of a V-ribbed belt (4), a protection layer (471) having elasticity and covering the pulley pressing part (407) on the side of the outer periphery of the crank pulley (2), a belt hold part (408) for hooking and holding the V-ribbed belt 4, and a belt pressing part (409) for pressing the V-ribbed belt (4) extending along the outer periphery of the crank pulley (2) against the outer periphery of the crank pulley (2).