An apparatus and method for measuring and reporting uplink load in a base station (BS) in a cellular mobile communication system are provided. The BS includes a rise over thermal (ROT) detector for measuring a ROT representing uplink load, and reporting information from which the ROT can be derived to a base station controller (BSC) via a standard interface. The ROT detector measures as background power the received power of the BS for a call-free period, the minimum of received power of the BS, or the minimum of received power of the BS measured for a predetermined time period. Then the ROT can be obtained by subtracting the background power from the received power of the BS.