To easily perform a loop back test by a high speed signal in a short time without requiring a special equipment by switching connection between ports by a switch, and performing the test by using a driver of a transceiver connected to the other port.

For example, at a test time of a receiver RCV2, an analog switch 110 is put in a connecting condition by a control signal CNT, and a control signal TXE1 of a driver DRV1 is enabled, and a control signal RXE1 of an RCV1 is disabled, and a TXE2 of a DRV2 is disabled, and an RXE2 of the RCV2 is enabled, and only the DRV1 and the RCV2 are put in an active condition, and a loop back test is performed by a signal passage using an output signal of the DRV1 as a test signal source to the RCV2. In this way, since a test of the RCVs 1 and 2 in a semiconductor device 100 is performed by using the DRVs 2 and 1 of a transceiver connected to the other port, a test signal generating tester is obviated.