To provide an air inflator device achieving efficient assembling work and uniform force of holding a flexible film member and a flexible pressure film and still offering compact and small figure.

The air inflator device comprises an air inflator body 1 having three members, namely, a body member 2 having an acoustic device 46, a balancing valve member 4 having a comparison chamber 9 and a switching valve member 5 having an operating portion. The three members are layered on one another and tightened with a tightening member 68 in such a manner that the comparison chamber 9 is located in line with the operating portion and the flexible film member 10 and the flexible pressure film 35 are held among the junction faces of the three members.