REDUCTION GEAR

A reduction gear W that is configured to reduce a rotation speed input to an input shaft , and output the reduced rotation speed from an output shaft, the reduction gear including: an inner trochoid that has a wavy curved surface formed on an inner circumferential side surface thereof; an inner trochoid holder that is designed to hold the inner trochoid ; an outer trochoid that has a wavy curved surface formed on an outer circumferential side surface thereof; a rotation restriction unit that is designed to restrict rotation of the outer trochoid around an axis thereof; and an output pin that is pinched between the outer circumferential side surface of the outer trochoid and the inner circumferential side surface of the inner trochoid