Fluid working machine

A fluid working machine comprising:

• cylinders that have a housing portion for accommodating a fluid;
• pistons that reciprocate in the cylinders due to pressure of the fluid;
• and
• a rotation axle that performs rotational motion in conjunction with reciprocating motion of the pistons, wherein
• the cylinders and the pistons are disposed circumferentially around of the rotation axle in the fluid working machine,
• the pistons comprise:
• a communication path that communicates with the housing portion;
• and
• an opposing concave recess provided in an opposing portion of the piston that faces a sliding surface of the rotation axle, and to which the fluid is supplied from the housing portion via the communication path, and
• the opposing concave recess is provided in the opposing portion such that a center position of a total force acting on the opposing portion of the piston from the fluid in the opposing concave recess is maintained at a position offset from a central axis of the piston in a direction opposite to rotation direction during the reciprocation of the pistons to prevent inclination of the pistons when a rotation axle is rotated.