When a press jig is inserted into a jig insertion hole, an O-ring attached to the outer peripheral surface of the press jig is prevented from being caught on an air supply port opening to the inner peripheral surface of the jig insertion hole and damaged. In a sealing pump-up device 10, the opening diameter of an air supply port 58 opening to the inner peripheral surface of a jig insertion hole 44 provided at one end of an air supply path 60 is set smaller than the strand diameters of an O-ring 72 and an O-ring 96. Consequently, the width at the edge of the air supply ports 58 on which the O-rings 72, 96 may possibly be caught can be made sufficiently smaller than the strand diameter of the O-rings 72, 96. When the O-rings 72, 96 pass on the inner peripheral side of the air supply ports 58 in a state of press contact with the inner peripheral surface of the jig insertion hole 44, the amount by which the O-rings 72, 96 are deformed (restored) in order to swell to the outer peripheral side so that a portion thereof fits into the air supply ports 58, can be reduced sufficiently.