A method of setting an actuator capable of accurately detecting a position of a piston using a plurality of sensor units is provided. The method includes a detection value acquisition step of moving a piston in a direction of an axis inside a cylinder and acquiring a detection value from each of a first sensor unit and a second sensor unit for each position of the piston, and a controlling sensor unit-setting step of setting a controlling sensor unit that is used for control of a two-way piston from among the first sensor unit and the second sensor unit on the basis of the detection values obtained for the first sensor unit and the second sensor unit.