To provide a communication channel decision circuit in response to a radio wave strength that can select and utilize a channel not disturbing communication of other wireless units by avoiding the same channel as a channel used by a similar wireless unit around the concerned wireless unit or a nearby channel.

The communication channel decision circuit is provided with a wireless section 102 that outputs a signal RSSI denoting a radio wave strength of a wireless signal received from an antenna 101 in a reception state and transmits the wireless signal to the antenna 101, a control circuit 221 that brings this wireless section 102 to the reception state even in the transmission state, a timing control circuit 221 that outputs timing signals LT21-LT24 by each of channels CH1-CH4 in the transmission timing, registers 211-214 that store a level of a signal outputted from the wireless section 102 in the reception state in response to the timing signals LT21-LT24, and a transmission reception control circuit 242 that compares the signal levels stored in the registers 211-214 and decides the transmission reception through one channel among a plurality of channels.