An air injection bathtub includes: a body part having a coupling recess formed depressedly on the bottom surface thereof; a plate part adapted to be fit to the coupling recess of the body part and having a connection groove formed depressedly on one side of the underside surface thereof, at least one air passing grooves formed depressedly on the underside surface thereof in a manner as to communicate with the connection groove and to pass the air supplied from the connection groove therethrough, and at least one air injection through-holes formed on the top surface of the plate part to inject the air passing through the air passing grooves into the body part; and a valve part disposed below the connection groove in a manner as to be open and closed through the air pressure supplied from the outside and to supply air to the connection groove.