The object is to provide a water heater capable of efficiently transmitting radiation heat of a burner to hot water in a hot water storage chamber with improved thermal efficiency. In the water heater, a second restriction part having a shallower depth than a first restriction part is arranged along a peripheral edge of a lower mirror plate of a hot water storage chamber with a protrusion part protruding in a ring shape toward the center side of the lower mirror plate. The protrusion part is further arranged between the first restriction part and the second restriction part, and a burner is positioned so that the burner combustion surface faces the protrusion part.