A belt attachment jig includes a jig body positioned such that a side surface faces a side surface of a pulley, and a belt guide portion located at one end of the side surface of the jig body and protruding along a circumference of the pulley, and having, in a surface on a base side, a holding surface for holding a belt. The belt guide portion being configured to guide the belt onto the holding surface and lead the belt out to a lateral side of the pulley, when fitted in a pulley groove of the pulley. The holding surface has a top at a portion on a side closer to the jig body, and is tilted obliquely downward in radial directions from the top and is curved in an inverted U shape along a lead-out direction of the belt so that an inner circumferential surface of the belt faces the jig body.