US Patent 9173408 Heating cooker

A water level sensor (91) is provided in an auxiliary tank (39) whose bottom portion communicates to a bottom portion of a pot (41) for generating steam and which is opened to the atmosphere. When water in the pot (41) keeps boiling and the stop time of a pump (35) reaches a predetermined time (e.g., 60 sec.), the pump (35) is driven for a predetermined time (e.g., 6 sec.) to supply water to the pot (41). This temporarily suppresses the boiling of water in the pot (41), lowering a steam pressure in a space formed by an external circulation passage (60), a heating chamber, and the pot (41). The water level in the auxiliary tank (39) then returns to a normal one, making it possible to correctly detect the water level in the pot (41).