The present invention provides a distortion compensating apparatus and method. The distortion compensating apparatus adaptively updates a distortion compensation coefficient for an amplifier (18) based on a difference between input and output signals of the amplifier (18), comprises: a distortion amount detector (291) which detects the amount of distort of an output signal of the amplifier (18); aparameter holder (14 and/or 23) which holds a parameter having been set therein; a parameter corrector (292) which corrects the parameter in such a manner that the distortion amount detected by the detector (291) is improved; and a distortion amount corrector (295) which corrects the distortion amount detected by the detector (291) in such a manner that the distortion amount is reduced by an offset amount according to an detection error. This arrangement makes it possible to accurately set the parameter relating to difference detection which is a factor of updating of distortion compensationcoefficients of the distortion compensating apparatus.