To easily and precisely receive data without wasting space and cost by continuously transmitting same packet data for plural times, detecting the respective RSSI received field level value signals of received packet data and setting packet data of the maximum RSSI signal to be received packet data.

A transmitter continuously transmits same packet data for plural times at prescribed time intervals. A receiver detects the RSSI signals for respective received packet data and sends them to a control part 3. The control part 3 adopts values converted into an average value and a dispersed value as RSSI values when the RSSI signals are sampled for plural times at an arbitrary part near the head part of the bit synchronous part of packet data as much as possible. The values are stored in a memory 3a with packet data. The control part 3 compares the RSSI values stored in the memory 3a and packet data whose value becomes the largest is adopted as received packet data.