Disclosed is a packet transmitting/receiving apparatus that receives a response packet to a transmitted request packet without fail. When a request packet is transmitted by a packet transmitter, a prediction of a response packet is made in reply to the transmitted request packet. When the response packet is received from a transmission medium, a comparator compares a portion of the packet received by a receiver with a portion of the packet and, only when they match, outputs the received packet. In this way, the expected response packet is received without fail. This enhances the reliability of the transmission medium.