A water heating device equipped with a housing, a fan and a chamber arranged in the interior of the housing, and screws. The housing has first and second side plates which oppose one another in a first direction and extend from the ends of a back plate along a second direction intersecting the first direction. An opening part is provided in the housing on the side opposite the back plate in the second direction. The fan has a discharge opening, a first flow passage extending along the first direction, and a first flange. The chamber has an intake opening, a second flow passage extending along the first direction, and a second flange. The first and the second flanges are secured by screws. In a planar view, the center axis of the screws is slanted such that a head portion is closer to the opening part than the tip-end portion.