A reception sensitivity is measured at a high precision. An access terminal function portion includes the transmitter part and receiver part of a communication terminal in a radio communication system. A path switch part effects switching so as to connect the input ends of receivers to antennas or to terminate them. The path switch part switches the paths of a signal from a transmitter and signals toward the receivers. An access point controller adjusts a packet error rate into a predetermined range, and obtains the reception sensitivity on the transmission power of the access terminal function portion after the adjustment.