PURPOSE: To highly efficiently transmit data by allowing a transmission control means to inform the completion of transmitting operation of at least one unit data to a processing means in accordance with transmission completion information outputted from a transmission means.

CONSTITUTION: When the succeeding data are sent from a terminal controller 202, the transmission control part 215 stores the leading address of a buffer corresponding to an untransmitted packet in a queue 217 and all the buffers indicated by the queue 217 are collectively requested to execute transmission processing. Consequently, the number of transmission processing requests and the number of times of transmission completion information can be reduced and the data transmission speed can be increased.