Provided is an on-chip monitor circuit mounted on a semiconductor chip that is equipped with a security function module for performing a security function process on an input signal and outputting a security function signal, the on-chip monitor circuit comprising a monitor circuit for monitoring signal waveforms of the semiconductor chip, wherein the circuit is provided with a first storage means for storing data that designates a window period in which to perform a test of the semiconductor chip, and a control means for performing control to operate the circuit during the window period, when a prescribed test signal is inputted to the security function module. By using the on-chip monitor circuit in a semiconductor chip of which security is required, security attacks, e.g., a Trojan horse or the like, intended to embed a malicious circuit in the production stage of security function module-equipped semiconductors chips, can be prevented.