PURPOSE: To prevent overheating of liquid in a container for heating by a method wherein when an amount of liquid in a container for heating is low and the temperature of liquid is increased to a value higher than a given temperature in a short time after the starting of heating, a heating means is stopped.

CONSTITUTION: When thirty seconds elapse after the starting of energization to a halogen heater 11, temperature detected by a thermistor 126 is stored as a reference temperature t0. A detecting temperature T detected when after the reference temperature t0 is detected, further thirty and sixty seconds elapse is detected as first and second initial stage temperatures, and it is discriminated whether each of temperature differences Δt1 and Δt2 exceeds 30deg. In this case, an amount of oil in a cooking container on which the thermistor 126 is mounted is improper and too low for cooking a fry, the rising speed of the detecting temperature T is increased and the temperature different Δt1 or Δt2 exceeds 30deg. Thereby, upon detection thereof, reporting takes place by means of a buzzer 128, and energization to the halogen heater 11 is stopped.