To provide an axial piston pump or motor superior in reliability and durability and capable of compact design, with pistons or a cylinder block smoothly operable under an operated condition with low viscosity fluid such as water as operating fluid.

The axial piston pump or motor comprises a swash plate 4 fixed to a casing 1, a slipper 10 for sliding the swash plate 4, the cylinder block 3 having a plurality of cylinder bores 3a equally spaced in the peripheral direction for rotation together with a main shaft 6, and the plurality of pistons 2 to be reciprocated in the cylinder bores 3a. It uses connecting rods 15 each of which has one end connected with the piston 2 via a resin layer and the other end connected with the slipper 10 via a resin layer.