PURPOSE: To propose an air bag structure which can suppress the variation of the respiration resistance according to the diving posture, as well as can reduce the respiration resistance in the diving time, in a respiration device for diving.

CONSTITUTION: In a respiration device 10 for diving, an air bag 25 for expiration and an air bag 26 for inspiration are housed to a B.C. jacket 12 to install the main body 11 of the device 10 to a diver. The air bags 25 and 26 are installed in the jecket 12 positioning at the places corresponding to the left and the right lungs of the diver. Since the air bags 25 and 26 are in the condition neighboring with the lungs of the diver constantly, the difference of elevation between the center of the air bags and the center of the lungs can be reduced, and the variation of the difference of elevation following the diving posture can be also suppressed. Consequently, the respiration resistance in the diving can be reduced, and the variation of the respiration resistance can be also reduced.