A verification support system for supporting logic verification of a circuit including a transmitter clock domain and a receiver clock domain, the transmitter clock domain, the system includes a detector for receiving data to be transmitted from the transmitter clock domain, and for detecting a fluctuation of the received data due to any timing fluctuation responsive to the transmitter clock. The system includes an identification unit to identify whether or not any fluctuation of the data determined by the detector is propagated to the output of the combinational logic on the basis of propagation of the received data through at least one of logic gates of the receiver clock domain to combinational logic so as to determine any fluctuation of data that is to be inputted to the combinational logic.