PURPOSE: To shorten a data transfer time to 2/N at the time of scan-in/out operation and to 1/N when data are scanned in the same register group after being scanned out by dividing a scan path equally by N into the same number of bits.

CONSTITUTION: Register groups 1A - 1N are divided equally into N groups which are equal in the number of bits, the serial-out terminal of a group (n-1) and the serial-out terminal of a group (n+1) and a scan-in data line 10 are connected to the serial-in terminal of a group (n) where 1 ≤ n ≤ N; and the serial-out terminals of the respective register groups are connected to a scan-out data line 11 through gates respectively and the terminal of the data line 10 is connected to the serial-out terminal of a scan data register 5. Then the scan operation mode of the register groups and address information on a register where data is to be scanned out are set in a scan address register 6 and scan-in/out operation is performed according to its contents. Consequently, the data transfer time can be shortened to 2/N at the time of scan-in/out operation and to 1/N when data are scanned in the same register group after being scanned out.