A method for retransmission data for a data transmission system in which a receiver transmits, when receiving data, a transmittal confirmation signal indicating whether the data is correctly received or not, and a transmitter refers to the transmittal confirmation signal and retransmits, when confirming that the data is not correctly received in the receiver, the data to the receiver, the method includes: at the transmitter, holding the transmitted data; keeping the holding of the transmitted data even after the transmitter confirms that the data is correctly received in the receiver by referring to the transmittal confirmation signal corresponding to the data and retransmitting, to the receiver, the data held therein in response to a request for retransmission of the data from the receiver.