A circuit board system is adapted to check a DUT (Device Under Test) and a communication device on a DUT board, check the connection between DUT and communication device and check connections of parts mounted on DUT board. The system, which tests a circuit board used when a DUT is tested using a tester, has a socket into which DUT is removably inserted; a communication device mounted thereon; first wires electrically connecting first signal terminals of DUT and the tester; and second wires electrically connecting second signal terminals of DUT, which are not electrically connected to the first signal terminals, and signal terminals of the communication device. A shorting board is inserted into the socket in place of DUT when the circuit board is tested, the shorting board having short-circuit wires electrically connecting the first wires and the second wires.