PURPOSE: To make the display easier to see, and at the same time, extend the life of a display tube by making the display tube perform a display motion by an appropriate luminous strength in response to the brightness of an installation environment or the existence/absence of a human body.

CONSTITUTION: On a control panel which is arranged on the front surface of a main body, a display tube 4 for the display of a cooking condition or display for time is provided. At the same time, an ultrasonic sensor 6 to detect a human body and a light detecting element 9 to detect the brightness of an environment are provided. A circumvention switch 10 is provided at a location which is on the side surface of the control panel, and is exposed when a door is opened. A control circuit 11 controls the luminous strength of the display tube 4 by a display driving circuit 4a, based on these detection signals. Based on the detection signals of the ultrasonic sensor 6 and light detecting element 9, the control circuit 11 sets a power connection duty ratio so that the luminous strength of the display tube 4 may become stronger when a person exists, and the level of the brightness of the environment is higher, for the luminous display. Thus, the display is made easier to see for user. At the same time, when it is not necessary, the display is done by a minimum power consumption, and the life of the display tube 4 is extended.