To provide a method for performing abdominal respiration nearly unconsciously though abdominal respiration is usually performed consciously.

Breathing in through the nose can be thought to have no problem. The problem is that one naturally breathes out through the nose but it is not abdominal respiration if one does not breathe out through the mouth. With that in mind, a hollow object 1 is provided with an inspiration preventing valve 2 so that one can breathe out through the mouth nearly unconsciously without consciously opening his or her lips and breathing out through the mouth and he or she can only breathe out through the mouth unconsciously.