CYCLOIDAL SPEED REDUCER, IN-WHEEL MOTOR DEVICE, AND VEHICLE MOTOR DRIVE DEVICE

A speed reducer part B of an in-wheel motor drive device (21) includes a casing (22), an input shaft (25) having one end arranged in the casing (22), disk-shaped eccentric members (25a and 25b) eccentric with respect to an axis O of the input shaft (25) and coupled to the one end of the input shaft, revolution members (26a and 26b) having a center part supported by outer circumstances of the eccentric members (25a and 25b) through a rolling bearing (41), to make a revolution motion around the axis O together with a rotation of the input shaft (25), an outer circumference engagement member (27) supported by the casing (22) and engaging with outer circumferential parts of the revolution members (26a and 26b) to cause the revolution members (26a and 26b) to make a rotation motion, and an output shaft (28) engaging with the revolution members (26a and 26b) to extract the rotation motion, in which the rolling bearing (41) has a lubricant oil hole (59) to supply a lubricant oil to a track surface (42a) being in rolling contact with a rolling body (44), and the lubricant oil hole (59) is arranged in a non-load range (360° - Æ) where a bearing load applied from the output shaft (28) and the outer circumference engagement member (27) to the revolution members (26a ad 26b) is not shared, in the track surface (42a) of the rolling bearing (41).