To provide a system for managing messages exchanged between a worker in the site of construction and a field management office in which a message can be delivered quickly and surely to the worker in the site of construction and post management of the transmission conditions of message can be performed efficiently.

Each field worker carries a portable communication unit K and a message management server S for receiving, storing and managing messages delivered from other units through a communication means, e.g. an LAN, along with address information and transmission timing designating information thereof is installed in a field management office. The message management server S transmits the message to a portable communication unit K designated by the address information at a timing designated by the transmission timing information.