A data processing apparatus includes a first frame processing unit that fragments a first input frame and identifies a head of the first input frame and outputs first head position information; a second frame processing unit that fragments a second input frame which is a redundant frame of the first input frame and is input asynchronously with the first input frame, identifies a head of the second frame, and outputs second head position information; a first and a second storage unit that receive and store the fragmented pieces of data output from the first and the second frame processing units respectively; and a fragmented data processing unit that reads the fragmented pieces of data out of one of the first and second storage units based on the first and second head position information and outputs the fragmented data.