To provide a heater cover for a water tank which is not burned even if a heater heats excessively.

A heater cover 1 for a water tank can house a heater 4 in the inside, is provided with a leading outlet 21 of a heater wire, and is made of fire retardant resin. The heater cover 1 is provided with a cylindrical member 2 having an opened side part 26 opened in the longitudinal direction and a plate-like membrane 3 which can freely be attached to and detached from the cylindrical member 2. Being attached to the cylindrical member 2, the plate-like member 3 covers the open side face part 26.