PURPOSE: To enable generation of O2 or suspension by placing a specific container on a right position or laying down sideways to bring an adduct of Na2 CO3.H2O2 into contact with a decomposing enzyme (catalyst) or non-contact.

CONSTITUTION: A given amount of an adduct 6 of Na2CO3.H2O2 is placed in a cylinder 5, air washing water 8 is added to an air washing cylinder 10, the upper part of the cylinder 5 is set, a cover part 3 of a closed container 1 is opened and this set is placed in the container 1. Then a given amount of an enzyme (catalyst) and a given amount of water are added to the container 1 and the cover part 3 is closed to generate an O2 gas. Then the prepared O2 gas is optionally sucked in an O2 suction tool 14. Then when generation of O2 is optionally suspended, the container is laid down sideways to make the side 17 of the container 1 on the bottom. When generation of O2 is restarted, the bottom 16 of the container is laid down and the container 1 is placed in a correct position.