A base station device for making radio communications with one or a plurality of mobile stations (102, 112), comprising: a pilot signal transmitter module for transmitting a pilot signal; and a transmit power determination module for determining a downlink transmit power of the base station device for each mobile station, the base station further comprises a receiver module for receiving a received power report from a mobile station (102, 112) connected to the base station device; the received power report is based on the intensity of the pilot signal received by the mobile station (102, 112) connected to the base station device; the transmit power determination module is configured to determine the downlink transmit power using a received power value contained in the received power report; and characterized in that the base station device further comprises: a holding module for holding a criterion value indicating a target channel quality value for mobile stations (102, 112) within a communication range of the base station (101, 111); a storage for creating quality data based on received power reports of the pilot signals received by the mobile station (102, 112) or mobile stations (102, 112) and storing the quality data; a transmit power determination module for creating a first representative value indicating average channel quality for the mobile station (102, 112) or mobile stations (102, 112) from the stored quality data and determining downlink transmit power of the base station device depending on a result of comparison between the first representative value and the criterion value; and a criterion value updating module for creating a second representative value indicating distribution of low channel quality and updating the criterion value depending on a result of comparison between the second representative value for mobile station quality data and the criterion value. a pilot signal transmitter module for transmitting a pilot signal; and a transmit power determination module for determining a downlink transmit power of the base station device for each mobile station, the base station further comprises a receiver module for receiving a received power report from a mobile station (102, 112) connected to the base station device; the received power report is based on the intensity of the pilot signal received by the mobile station (102, 112) connected to the base station device; the transmit power determination module is configured to determine the downlink transmit power using a received power value contained in the received power report; and a holding module for holding a criterion value indicating a target channel quality value for mobile stations (102, 112) within a communication range of the base station (101, 111); a storage for creating quality data based on received power reports of the pilot signals received by the mobile station (102, 112) or mobile stations (102, 112) and storing the quality data; a transmit power determination module for creating a first representative value indicating average channel quality for the mobile station (102, 112) or mobile stations (102, 112) from the stored quality data and determining downlink transmit power of the base station device depending on a result of comparison between the first representative value and the criterion value; and a criterion value updating module for creating a second representative value indicating distribution of low channel quality and updating the criterion value depending on a result of comparison between the second representative value for mobile station quality data and the criterion value.