The present invention provides a standard cell and a scan flip flop circuit capable of introducing a scan test also to a system LSI having an ACS circuit. One standard cell is configured by: a 3-input selection circuit for selecting one signal from three input signals; and a flip flop circuit. The 3-input selection circuit receives a control signal and a test signal at its control input part and its first input part, respectively. First and second signals are supplied to second and third input parts, and a selection signal is supplied to a selector input part. On the basis of the control signal and the selection signal, any of the signals input to the first to third input parts is output from the output part.