A transmission power control method, a wireless communication system and a terminal apparatus which can reduce radio interference to each terminal apparatus installed into peripheral cars other than the communication counterpart are provided. In wireless communication between at least two movable terminal apparatuses, a terminal apparatus which has received a predetermined wireless signal transmitted with a known electric power from another terminal apparatus measures its received power and sets a numerical value of transmission power when transmitting information to the other terminal apparatus according to the measured value of the received power.