A packet processor for processing an input packet includes an information generator for generating process control information for processing the input packet, an internal packet generator for receiving the input packet as an packet to be processed and adding the process control information to the packet to be processed to produce an internal packet, an internal packet processor for processing the internal packet supplied from the internal packet generator on the basis of the process control information added to the internal packet, and a packet transmitter for extracting an output packet from the internal packet processed by the internal packet processor to transmit the output packet. The packet processor can reduce the amount of communication between modules even when the packet processor includes plural modules.