The multi-initiator control unit for performing packet-unit communication with each of a plurality of devices connected via a transmission line includes: a packet filter for analyzing a received packet and outputting the results; a plurality of command control circuits each for controlling a command processing sequence performed with the corresponding device; a multi-control circuit for giving sequence execution permission to one of the plurality of command control circuits; and a packet processing circuit for generating a packet containing information output by the permission-given command control circuit and outputting the packet for transmission, and also outputting a received packet according to the analysis results output by the packet filter.