To provide an on-vehicle portable telephone system which can reduce the dangers caused by the incoming calls and the talking when driving an automobile and also can quickly inform of these dangers.

A control block 3a decides whether an automobile is running or not based on the speed information on the automobile received from an engine control unit 4 and the operating state information on a parking brake received from a parking brake unit 5. If a portable telephone unit 2 receives a call while the automobile is running, the block 3a functions to stop the ring tones of the unit 2 or reduces these tone levels and to count the calls received during running. A sound recording/reproducing unit 3 gives a recorded message to the opposite party side to tell an under-driving state of the automobile and then records the message of the opposite party side. When the automobile stops, the message of the opposite party side recorded by the unit 3b is reproduced through a speaker (sp) based on the number of received calls.