PURPOSE: To provide the bath hot water circulating passage structure in the bubble generating bathtub, in which the hot water circulating passage consists of an air ventable structure, and an air lock generated in the flow passage can be prevented.

CONSTITUTION: In the bubble generating bathtub constituted so that between a bathtub main body 1, and a circulating pump P installed on the outside of the bathtub main body 1, a bath hot water circulating passage B consisting of a bath hot water suction passage B1 and a bath hot water forced feeding passage B2 is provided, and to an opening part of the bath hot water forced feeding passage B2, jetting nozzles 4, 5 are attached, and also, to the bath hot water circulating passage B, an air intake part 27 is allowed to communicate and connected, and from the nozzles 4, 5 bath hot water in which bubbles are mixed can be jetted into the bathtub main body 1, on the bath hot water forced feeding passage B2 side of the circulating pump O, an air vent valve V is attached at a position above an impeller chamber P1 of at least the pump P.