To establish a compacted construction and widen the degree of freedom in designing the gear dimensions, etc., of a reduction gear.

A swash plate 30 is installed in the open face at one end of a motor housing 4, and a power generating mechanism 32 is installed inside the motor housing 4, and a reduction gear input shaft 5 joined with a motor output shaft 38 is allowed to penetrate the center of the swash plate 30 and protrude to outside the motor housing. Coaxially with the input shaft 5, a second sun gear 14 is installed, and a rotary frame 6 having an internal gear 8 consolidatedly is rotatably fitted through bearing 7 on one end of the motor housing, and a second planetary gear 16 is installed between the second sun gear and internal gear, and through the second planetary gear, the rotation of the second sun gear is transmitted to the internal gear so that the rotary frame is rotated deceleratively. In this swash plate type hydraulic motor 1 equipped with planetary reduction gear, a plurality of bosses 40 consolidated with the swash plate 30 are formed protrusively on that surface of swash plate 30 located on the side opposite the slope 31, and the second planet gear 16 is held rotatably by the bosses 40.