PURPOSE: To improve the cooking function and increase the cookable menu by providing a function which controls respectively the electrical power for both of an upper and a lower heater, and adjusts the electrical power ratio of the upper heater to the lower heater for preparing the optimum heating condition required for each cooking menu.

CONSTITUTION: An upper heater electrical power control device 7 connected with an upper heater 4 and a lower heater electrical power control device 8 connected with a lower heater 5 are controlled according to each heating condition for predetermined cooking menu by the selection of a cooking menu selector 6, that is, each electrical power control devices 7, 8 are formed to perform the ON-OFF duty control as shown by an output waveform 9, and formed as the ON/OFF ratio is made to be designated by the cooking menu selector 6. When the ON/ OFF ratio is made small, the electrical power for the heater is decreased. The structure is composed as the electrical power control for the upper heater 4 and the electrical power control for the lower heater 5 are controlled individually, also each input electrical power of the upper and the lower heaters 4, 5 for adjusting the inside temperature of a chamber is adjusted simultaneously.