A de-spreading device for a spread spectrum communication system includes a first and a second correlator assigned to a regular and a power-saving operation mode, respectively. The first correlator performs sampling with a regular operational clock while the second correlator performs sampling with an operational clock higher in rate than the regular operational clock for thereby saving power. The regular or the power-saving operation mode is selected in accordance with radio channel quality estimated on the basis of a peak value detected from a correlation value, which is output from the first or the second correlator. De-spreading can therefore be implemented by an optimum operational clock matching with radio channel quality while consuming a minimum of current.