A bent axis type axial piston pump or motor wherein the cylinder block is rotatable in synchronizm with the torque plate about an axis inclined relative to the axis of rotation of the torque plate. The shaft of the torque plate passes through the inclined cylinder block without mutual mechanical interference and is supported by bearings at the opposite sides of the casing. The torque plate and the cylinder block are connected by a mechanism which ensures exact synchronization of rotation of the two members. A static pressure balance is established between the working fluid acting on the opposite sides of the torque plate, the cylinder block and the pistons, respectively. The angle of inclination of the cylinder block with respect to the shaft can be changed thereby to change the capacity of the pump or motor. The pump or motor of this invention may be provided in a tandem type.