A transmitter for use in a variable-length serial burst data transmission system having the transmitter and a receiver that are connected by at least two data signal lines and a burst start line includes a dual-rail encoder and a burst start signal receiving part. While transmitting variable-length serial data, the dual-rail encoder encodes each bit of the serial data into a corresponding symbol, inserts a null symbol delimiting the data symbols, and sends out the symbols via the two data signal lines to the receiver. For a period of non-transmission state, the transmitter sends out an invalid symbol representing a non-transmission state via the two data signal lines to the receiver. The burst start signal receiving part receives a burst start signal, which indicates a start of burst transmission of the variable-length serial data, via the burst start line from the receiver. In the transmitter, the dual-rail encoder sends out the null symbol to the receiver at the start of the burst transmission, and performs the burst serial transmission of the variable-length serial data in response to the burst start signal sent out by the receiver.