A data processing apparatus includes a decision section that determines a predetermined plurality of channels of original data and a predetermined channel of correction data based on data of received signals; an exclusive OR circuit that calculates an exclusive OR upon the channels of the decided data; a signal quality decision section that detects signal quality of received data on each channel; and a correction section that replaces a channel of data whose channel has a worst detection result as detected by the signal quality detection section with the result of the exclusive OR calculation when the result of the calculation is other than "0". The signal quality detection section calculates a mean signal quality and an instantaneous signal quality that are used by the correction section to determine the worst channel.