To simplify and miniaturize structure of a coupling device by complexly composing a fluid pressure cylinder for connecting and separating a male joint and a female joint of the coupling device with a guide supporting member supporting and guiding the male and female joints.

This device is provided with a guide supporting member 4 supporting and guiding a female joint 5 and a hydraulic cylinder 6 moving the female joint 5 for connecting and separating both joints 3, 5 with reference to the male joint 3. A cylinder hole of the hydraulic cylinder 6 is formed on the guide supporting member 4, the female joint 5 is equipped to the cylinder hole, and fluid pressure is acted on a main body case 30 forming the outside shape part of the female joint 5, which enables driving the female joint 5 to move.