To provide a water heater capable of suitably preventing or suppressing drain in a drain pipe from flowing into a bathtub even if the drain pipe is damaged, when a double pipe structure in which the drain pipe is inserted to a bath pipe is adopted.

The water heater WH includes a drain storage part 3 for storing the drain generated according to heat recovery using a heat exchanger and a drain pump P3 for making the drain stored in the drain storage part 3 flow into the drain pipe 6 and for guiding the drain to a predetermined drainage place. The water heater includes a double pipe structure part D in which the drain pipe 6 is inserted into the bath pipe 7A and the termination side part 6a of the drain pipe 6 is drawn out from the bath pipe 7A. The drain pump P3 is provided for the termination side part 6a of the drain pipe 6, and the inside of the drain pipe 6 becomes a negative pressure status when the drain pump P3 is driven.