PURPOSE: To provide a pressure oil supply device which is so installed as to advance to and retreat from to a port of a pressure oil supply/discharge device and which can reduce the mixing of air and contamination from a pressed portion of the pressure oil supply device capable of pressing.

CONSTITUTION: A pressure oil supply device is so pressed as to advance to and retreat from semispherical ports 36 of pressure oil supply/discharge devices 11, 12 connected to a hydraulic shaft coupling which are brought in a connection condition through sealing of the received pressure oil, and in a released condition through discharging of the sealed pressure oil. A piston 64 is slidably arranged inside a cylinder 63. A valve seat member 67 is provided on a leading end of a rod 65 of the piston 64 abuttingly against the semispherical ports 36. Oil passages 70, 69 are formed for penetrating the rod 65 from the valve seat member 67. A throttle part 71 is arranged on an outlet side of the oil passage 70, while an air nozzle 74 is arranged opposingly to the semispherical ports 36.