Position detecting device

A position detecting device for detecting a position of a workpiece by ejecting a pressure fluid supplied from a pressure fluid supply source from a detection nozzle with respect to a detection surface of the workpiece, and detecting a back pressure of the pressure fluid, comprising:

• a device main body into which the pressure fluid supplied from the pressure fluid supply source is introduced;
• and
• an attaching/detaching mechanism that enables attachment and detachment with respect to the device main body, including an internal nozzle that delivers, toward a side of the 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;
• a communication hole that communicates with a detection passage is disposed in a reduced diameter section along a radial direction of the attaching/detaching mechanism;
• and
• a fluid introduction space which communicates with the detection passage via the communication hole at a location in a vicinity of the reduced diameter section in a mounting section, when the attaching/detaching mechanism is mounted,
• wherein the position detecting device further comprises a detection passage side pressure sensor for detecting the back pressure, by detecting a pressure of the pressure fluid introduced from the detection passage into the fluid introduction space via the communication hole.