A heating cooking device, comprising: a heating chamber for housing a food product; a high-frequency wave generating device for generating a high-frequency wave that heats said food product; a machine chamber provided adjacent to said heating chamber; an air supply port provided in a partition wall that separates said heating chamber and said machine chamber; an air supply fan provided in said machine chamber, for supplying air to said heating chamber through said air supply port; an air supply damper provided in said machine chamber, for opening and closing said air supply port; and a control unit provided in said machine chamber, for controlling an operation of said high-frequency wave generating device, said air supply fan, and said air supply damper, wherein said control unit drives said air supply fan and brings said air supply damper into an open state during high-frequency heating of said food product, and said control unit brings said air supply damper into a closed state simultaneously with completion of high-frequency heating of said food product or immediately before or immediately after the completion, and maintains air supply fan operation for a prescribed time period after closure of the air supply damper characterised in that the heating cooking device further comprises a power supply monitoring unit monitoring a supply state of an external power supply; and a backup power supply unit capable of supplying power for a prescribed time period, when the external power supply is stopped, wherein when stop of the external power supply is detected by said power supply monitoring unit during high-frequency heating of said food product, said control unit brings said air supply damper into the closed state by power supply from said backup power supply unit. a heating chamber for housing a food product; a high-frequency wave generating device for generating a high-frequency wave that heats said food product; a machine chamber provided adjacent to said heating chamber; an air supply port provided in a partition wall that separates said heating chamber and said machine chamber; an air supply fan provided in said machine chamber, for supplying air to said heating chamber through said air supply port; an air supply damper provided in said machine chamber, for opening and closing said air supply port; and a control unit provided in said machine chamber, for controlling an operation of said high-frequency wave generating device, said air supply fan, and said air supply damper, wherein said control unit drives said air supply fan and brings said air supply damper into an open state during high-frequency heating of said food product, and said control unit brings said air supply damper into a closed state simultaneously with completion of high-frequency heating of said food product or immediately before or immediately after the completion, and maintains air supply fan operation for a prescribed time period after closure of the air supply damper characterised in that the heating cooking device further comprises a power supply monitoring unit monitoring a supply state of an external power supply; and a backup power supply unit capable of supplying power for a prescribed time period, when the external power supply is stopped, wherein when stop of the external power supply is detected by said power supply monitoring unit during high-frequency heating of said food product, said control unit brings said air supply damper into the closed state by power supply from said backup power supply unit.