To calculate a proper amplification factor so as to prevent a target power level from being exceeded as the result of amplifying the power level of a received signal even in the case of varying the number of users during transmitting signals.

Judging parts 111 to 113 judge a user transmitting a signal. A control part 104 specifies the number of the users transmitting the signal by the judgement result, calculates the power level of the received signal per user based on the power level of the received signal and the number of the users transmitting the signals, and estimates a power level when all the users are in transmission during communication based on the calculated power level and the number of the users in communication.