An embodiment of the invention provides a circuit for detecting a malfunction generation attack, including: at least one sensor circuit adapted to detect a radiation of a light; and a detection circuit for detecting an intermediate voltage between a voltage corresponding to a High level and a voltage corresponding to a Low level in accordance with an output from the at least one sensor circuit, and outputting a detection signal. At least one sensor circuit has an output node a level at which is changed in accordance with the radiation of the light, and outputs a signal corresponding to the level at the output node which is changed in accordance with the radiation of the light. The detection circuit outputs the detection signal when a level of the output signal from the at least one sensor circuit reaches a level previously set.