To conduct the test of a mobile set under an environment actually used and to sharply reduce number of workers for the test.

One-side terminals of control lines 1041-104N are connected to external connection terminals 1031-103N of 1st to N-th portable telephone sets 1021-102N, and the other terminals are connected to a mobile set controller 101. The mobile set controller 101 sends a control signal to the control lines 1041-104N to confirm an originating/incoming call of the portable telephone sets 1021-102N, send a test signal in a state set to a speech state and checks the reception state of the looped-back test signal to check the speech quality of the 1st to N-th portable telephone sets 1021-102N.