PURPOSE: To easily turn ON or OFF for the generation of air bubbles by a bather in a household bath and to freely increase/decrease the generating quantity of the air bubbles by fitting a packing to interrupt air to be sucked from a hole part to the base edge of an operating cylinder and adjusting air quantity to be mixed in at the exit side of an orifice by the forward/backward movement of the operating cylinder.

CONSTITUTION: For a hot water supplying port 7 to return purified hot bath water to the inside of a bathtub 1, the flow velocity of the hot bath water to flow in is increased at the exit side of an orifice 18 having a diameter smaller than that of a line 9D by the orifice 18, and the hot bath water is made into a jet stream and vigorously discharged in the bathtub 1. At this time, when a knob part 22A protruding in the bathtub 1 is rotated, and an operating cylinder 22 is moved, a packing 23 contacted with a hole part 21 by pressing is separated from the hole part 21, the air flows in toward the jet stream of the hot bath water at the exit side of the orifice 18, and while the jet stream rolls and mixes the air in itself, the jet stream generates a large quantity of fine air bubbles having a massaging effect and ultrasonic waves accompanying the generation of the air bubbles in the hot bath water. The generating quantity of these air bubbles and ultrasonic waves can be adjusted by adjusting the air quantity according to the rotating way of the operating cylinder 22.