To arrange a case on a bathtub at an arbitrary place and to miniaturize the case to collectively house necessary parts in the case.

In a circulating hot water purifying apparatus for bath, a case is almost formed into a rectangular form long left and right on a plan view. A pair of left and right pipe connection parts 10, 11 are arranged to the front part of the case 3. The circulating pump 2 connected to the underside pipe connection part 10 is arranged up and down at an almost central part in the front and rear direction in the case 3 behind of the pipe connection part 10. The heater 41 connected to the pipe connection part 11 on its lower side is up and down arranged to the pipe connection part 11 at an oblique position on the side opposite to the circulating pump 7. A rising pipe 33 connected to the lower side of the circulating pump 2 at its lower end and connected to the upper end of the heater 41 at this upper end is arranged between the circulating pump 2 and the heater 41 but behind the segment L connecting the circulating pump 2 and the center of the heater 41.