To shorten the time needed for estimating a spread code in an initial synchronization mode, without deteriorating the estimation accuracy with regard to a receiving device of a code division multiple access(CDMA) communication system.

This estimating device consists of a standby selection averaging means 105, which averages the correlation value in a small number of averaging times, a candidate code selection means 106 which selects the numbers of several spread codes having a large average correlation value as correct spread code candidates, a main selection averaging means 107 which averages the correlation value of each candidate code over a sufficient number of averaging times, and a maximum value detection means 108 which detects the number of the spread code that has the maximum correlation value.