Provided is an air spraying device for a bathtub, wherein the structure of the device is improved such that unwanted matter such as scale does not remain inside the spraying device. To this end, the present invention is an air spraying device for a bathtub, which is provided in the floor of the bathtub and sprays air supplied from the outside into the bathtub so as to make bubbles, wherein the device comprises: a main body plate which is shaped as a flat plate having a predetermined length and is provided in the floor of the bathtub； a linking groove which is obtained by forming a depression on one side of the bottom surface of the main body plate； a valve which is installed underneath the linking groove and operates in such a way as to open and close due to the pressure of air supplied from the outside such that air is supplied to the linking groove； at least one air-passing groove which is (are) obtained by forming a depression (depressions) in the bottom surface of the main body plate and is (are) linked through to the linking groove, in which state a supply of the air supplied to the linking groove is received and allowed to pass through； at least one air spray hole which is (are) formed connecting through to the upper surface of the main body plate and sprays (spray) the air passing through the air-passing groove(s) into the bathtub； and a baseplate which covers the bottom surface of the main body plate.
