Abstract: The present invention relates to a message-passing computer system and a packet-switched interconnection network. The message transfer apparatus in a packet-switched interconnection network includes a message send controller controlling a send procedure in which messages requested by a processor are sent via an output port, and a timer enabled by an output signal of the message send controller and generating a timeout signal. A buffer unit is connected to the message send controller and is composed of a message buffer having four buffers and a data buffer. A local bus controller connects the message send controller and the buffer unit to the local bus and controls a transfer request and a transfer response to the local bus. An output port controller connected to both the message send controller and the buffer unit controls the output port which sends a packet to an interconnection network.