An error addition apparatus receives a data signal D having a frame format having a specific signal inserted into its front, adds errors to the data signal D, and outputs a resulting signal. The apparatus has an error addition regulation unit for receiving a frame synchronization signal F, indicative of a timing at which the front of the frame of the data signal has been inputted, and regulating the errors such that the errors are added to positions other than a region of the specific signal. Accordingly, errors are not added to a specific signal.