The present invention relates to a belt attachment tool used in order to further wind, around a third pulley (3), a belt which has been wound around a first pulley (1) and a second pulley (2). The belt attachment tool is provided with: a side surface part (10); an attachment part (11); a first belt-holding part (14); and a second belt-holding part (15). The second belt-holding part (15) is disposed such that an intersection point (F) between a first extension line (L1), which extends the belt wound around the first belt-holding part (14) from the outer periphery of the second pulley (2), and a second extension line (L2), which extends the belt wound around the second belt-holding part (15) from the outer periphery of the first pulley (1), is positioned further towards the front side of the third pulley (3) in the rotation direction (A) than a centre line (L3) joining the centre (1S) of the first pulley (1) and the centre (3S) of the third pulley.