Abstract: A method for controlling a cavity lamp of a microwave oven has a step of determining whether a door is opened. A cooking state is identified by determining whether a cooking key of a key input portion is selected when the door is opened. Whether the cooking cancellation key of the key input portion is selected when the door is not opened in the cooking state is identified. A cavity lamp is turned off when the cooking cancellation key is selected. Whether an open time of the door passes beyond an established predetermined time in advance is determined. The cavity lamp is turned off when the open time of the door passed beyond the predetermined time. Therefore, the cavity lamp which is turned on when a door is opened is turned off automatically or manually so that life of the cavity lamp is lengthened and loss of electric power is reduced.