A data transmission method etc. is provided. At a transmitting side, if a frame contains transmission data, frame data containing the transmission data and a calculated error-detecting code is generated. If the frame contains no transmission data, frame data containing neither transmission data nor an error-detecting code is generated. At a receiving side, one or more final bit positions of the frame data are assumed in the frame, transmission data and an error-detecting code are assumed in the frame, and the error-detecting code of the assumed transmission data is calculated. If there is a position where the assumed error-detecting code matches the error-detecting code calculated based on the assumed transmission data, it is decided that the position is the final bit position. Otherwise, it is decided that the frame contains no transmission data or that the received frame data contains an error.