A disclosed power level measuring device includes a power calculator for calculating power values based on correlation values between a received signal and known signals, for each of sampling times within a predetermined period; a time divider for switching connection of input signals, responding to time slots allocated to each of plural cells; an accumulator connected to the time divider, for accumulating the power values; a detector for detecting at least one sampling time whose accumulated value is greater than a threshold; a memory connected to the time divider, for storing the power values; and an outputting unit for outputting a measured power level, based on the stored power value corresponding to the detected sampling time.