A position detecting device is equipped with a device main body into which a pressure fluid supplied from a pressure fluid supply source is introduced, and an attaching/detaching mechanism that enables attachment and detachment with respect to the device main body. The attaching/detaching mechanism includes an internal nozzle that delivers, toward the side of a detection nozzle, the pressure fluid supplied to the device main body, and a detection port that supplies, to the detection nozzle, the pressure fluid delivered from the internal nozzle.