The spot welding gun cooling water circulation apparatus of the invention, blocking the cooling water from the water source with the valve, the spot welding gun removably to the front end of the welding arm that is installed so that it extends back in contact with the attached welding tips rear inlet pipe and outlet pipe as a spot welding gun cooling water circulation device comprises a, between the outlet pipe and the drainage holes, and the drainage holes, only the cooling water to flow to check at least one of the outlet check valve and the at least one drain placed in series towards the valve, the outlet check valve and drainage check valve in the connection pipe between the cylinder to be reciprocated so that the alternating negative pressure and positive pressure, a pressure switch for detecting the pressure at any position between to the cylinder from the shut-off valve, and the cylinder, the cut-off reciprocating is initiated by a blocking signal of the valve, the pressure sensed by the pressure switch is reciprocating is stopped by the pressure signal that is generated when less than a predetermined pressure, by the reciprocating of the cylinder, if a negative pressure is generated in the connecting pipe , only the outlet check valve opens and the cooling water is sucked into the connection pipe from the outlet conduit, if a positive pressure is generated in the connecting pipe, the drainage check valve only opens characterized in that the cooling water is discharged from the hole drain operation so that the connection pipe.