PURPOSE: To provide an air charging device to facilitate recharge of gas and suitable for an expansion type lifesaving apparatus by engaging an actuating cylinder blocking a sealed surface of a bomb with an actuating shaft, a ball and an actuating cylinder storage cylinder and connecting and disconnecting the actuating cylinder storage cylinder to and from a valve base outer shell.

CONSTITUTION: When an air charging device 1 is soaked in water, as water flown in the inside from an admission port 29 of water lowers strength of a binding material 28 and cuts it, a driving bar 22 loaded by a driving spring 21 disassembles a stopper 24, and a head end of the driving bar 22 gives impulsive force to an operation part 13. Then, as an operation shaft 12 receiving the impulsive force compresses an operation bearing spring 14 and it is pushed in, a ball 16 can easily approach the side of the operation shaft 12. At this time, as an actuating cylinder 8 is pushed by gas pressure applied from a gas bomb 30 in the A direction, the ball 16 moves toward the side of an inner cavity and engagement by a prohition part 17 is released. Consequently, an air inlet passage is opened, gas in the bomb 30 is supplied to a floating body through a suction pipe 31 and expands a lifesaving apparatus.