A wiring board for use in mounting an electronic component includes a switch element portion interposed in a signal transmission line including a wiring layer linked to an electrode terminal of the electronic component. The switch element portion has such a structure as to change the shape thereof depending on a temperature, and to disconnect the signal transmission line when the temperature exceeds a predetermined temperature. A conductor layer which constitutes a portion of the signal transmission line is formed at the bottom of a cavity formed in an electronic component mounting surface side of the wiring board. One end of the switch element portion is fixedly connected to the wiring layer, and another end thereof is in contact with the conductor layer when the temperature is equal to or lower than the predetermined temperature.