To mechanically take in and out air by easily push-opening an inner valve of an air injection hole in a float or the like, with reduced human labor, without deforming the inner valve of the float or the like by hand.

The inner valve in the air injection hole can be push-opened at its inclination angle by inserting the tip of this device serving as an inclined tip, an injection port and an intake port into the air injection hole of the float or the like. Air inside the float or the like can be removed through a hole serving as the injection port and the intake port arranged in a tip part by starting a vacuum pump or a cleaner from that state. The air is injected into the float or the like by using a compressor instead of the vacuum pump.