A wireless communication system composed of a wireless terminal, a plurality of base stations (101, 102, 103) configured to perform wireless communication with the wireless terminal, and a server connected to the base stations via a network, the wireless terminal comprising: a wireless communication means for communicating with the base stations (101, 102, 103); a position data transmission means for transmitting a signal containing position data of the wireless terminal to the server via the wireless communication means; and a transmission power control means for switching the wireless communication means between a first mode in which the wireless communication means transmits data at normal power and a second mode in which the wireless communication means transmits data at power smaller than the normal power, and the server comprising: means for determining the position of the wireless terminal from the position data received from the wireless terminal; a storage means for storing position data of the wireless terminal transmitted from the wireless terminal; a base station designating means for designating one of the base stations (101, 102, 103), which is close to the wireless terminal in accordance with the position data, when the wireless terminal is set to the second mode; and a decision means for determining that the base station designated has a problem if the server does not receive the signal the wireless terminal has transmitted in the second mode, wherein the transmission power control means switches the wireless communication means from the first mode to the second mode in accordance with a control signal received from the server via the wireless communication means. a wireless communication means for communicating with the base stations (101, 102, 103); a position data transmission means for transmitting a signal containing position data of the wireless terminal to the server via the wireless communication means; and a transmission power control means for switching the wireless communication means between a first mode in which the wireless communication means transmits data at normal power and a second mode in which the wireless communication means transmits data at power smaller than the normal power, and the server comprising: means for determining the position of the wireless terminal from the position data received from the wireless terminal; a storage means for storing position data of the wireless terminal transmitted from the wireless terminal; a base station designating means for designating one of the base stations (101, 102, 103), which is close to the wireless terminal in accordance with the position data, when the wireless terminal is set to the second mode; and a decision means for determining that the base station designated has a problem if the server does not receive the signal the wireless terminal has transmitted in the second mode, means for determining the position of the wireless terminal from the position data received from the wireless terminal; a storage means for storing position data of the wireless terminal transmitted from the wireless terminal; a base station designating means for designating one of the base stations (101, 102, 103), which is close to the wireless terminal in accordance with the position data, when the wireless terminal is set to the second mode; and a decision means for determining that the base station designated has a problem if the server does not receive the signal the wireless terminal has transmitted in the second mode, wherein the transmission power control means switches the wireless communication means from the first mode to the second mode in accordance with a control signal received from the server via the wireless communication means.