A scan control method for a circuit device connected with a first bus and having a test access port controller, including setting information indicating a register to be scanned in the circuit device, a number of scan shifts and a scan start via a second bus different from the first bus, and generating based on the information set, by using a sequencer, a signal replacing a test mode signal and a test reset signal transferred via the first bus during testing of the circuit device, and supplying the signal to the test access port controller.