1. An information processing apparatus for processing a transmission message among a plurality of sites that are connected to one another via a network, comprising: a message reception part that receives a message to thereby execute a prescribed piece of reception processing; a rule accumulation part that accumulates therein rules for executing message processing; a message conversion part that executes message conversion processing according to the rules that have been accumulated in said rule accumulation part; and a message transmission part that executes a prescribed piece of transmission processing of the post-conversion message.