To prevent the generation of remarkable tensile force on a belt for driving a holder having a massage roller.

Concerning this instrument, the holders provided with the massage rollers are linked to a belt 15 to be traveled and driven by a driving device 10, and the holders are interlocked by reciprocatively driving the belt. In this case, the driving device has a pair of pulleys 14 around which both the end parts of the belt are respective wound, the belt is traveled by feeding out the belt wound around one driving pulley when taking up the belt around the other driving pulley, and the driving pulley is formed in the shape of polygon having a flat part 14a on the outer peripheral face.