A hydraulic machine of a radial-piston type, comprising: a rotor shaft extending in an axial direction of the hydraulic machine; a ring cam extending in a circumferential direction of the hydraulic machine and configured to rotate together with the rotor shaft; and a piston assembly configured to perform reciprocating motion in accordance with rotation of the ring cam, wherein the ring cam comprises a plurality of cam segments (58,60,80) arranged in the circumferential direction, wherein at least one adjacent pair of the plurality of cam segments (58,60,80) includes a preceding segment and a following segment disposed subsequent to the preceding segment in a rotational direction of the ring cam, wherein the preceding segment has a first engagement portion protruding toward the following segment at a trailing end portion of the preceding segment, wherein the following segment has a second engagement portion protruding toward the preceding segment at a leading end portion of the following segment and being engageable with the first engagement portion of the preceding segment, wherein the first engagement portion has a first cam surface in the trailing end portion of the preceding segment, the first cam surface facing the piston assembly, and the second engagement portion has a second cam surface in the front end portion of the following segment, the second cam surface facing the piston assembly, the first cam surface being disposed closer to the piston assembly than the second cam surface with respect to a radial direction of the hydraulic machine at a front end of the second cam surface, wherein the first cam surface and the second cam surface intersect each other in an engagement region of the first engagement portion and the second engagement portion, and wherein each of the first cam surface and the second cam surface has a convex curved surface bulging toward the piston assembly, characterized in that a first tangent T 1 is closer to the piston assembly than a second tangent T 2 at a downstream side of a position P 0 with respect to a rotational direction of the ring cam, where the position P 0 is a position where the first cam surface and the second cam surface intersect with each other, the first tangent T 1 is a tangent to the first cam surface at the position P 0, and the second tangent T 2 is a tangent to the second cam surface at the position P 0. a rotor shaft extending in an axial direction of the hydraulic machine; a ring cam extending in a circumferential direction of the hydraulic machine and configured to rotate together with the rotor shaft; and a piston assembly configured to perform reciprocating motion in accordance with rotation of the ring cam, wherein the ring cam comprises a plurality of cam segments (58,60,80) arranged in the circumferential direction, wherein at least one adjacent pair of the plurality of cam segments (58,60,80) includes a preceding segment and a following segment disposed subsequent to the preceding segment in a rotational direction of the ring cam, wherein the preceding segment has a first engagement portion protruding toward the following segment at a trailing end portion of the preceding segment, wherein the following segment has a second engagement portion protruding toward the preceding segment at a leading end portion of the following segment and being engageable with the first engagement portion of the preceding segment, wherein the first engagement portion has a first cam surface in the trailing end portion of the preceding segment, the first cam surface facing the piston assembly, and the second engagement portion has a second cam surface in the front end portion of the following segment, the second cam surface facing the piston assembly, the first cam surface being disposed closer to the piston assembly than the second cam surface with respect to a radial direction of the hydraulic machine at a front end of the second cam surface, wherein the first cam surface and the second cam surface intersect each other in an engagement region of the first engagement portion and the second engagement portion, and wherein each of the first cam surface and the second cam surface has a convex curved surface bulging toward the piston assembly, characterized in that a first tangent T 1 is closer to the piston assembly than a second tangent T 2 at a downstream side of a position P 0 with respect to a rotational direction of the ring cam, where the position P 0 is a position where the first cam surface and the second cam surface intersect with each other, the first tangent T 1 is a tangent to the first cam surface at the position P 0, and the second tangent T 2 is a tangent to the second cam surface at the position P 0.