To provide a program distributing method capable of improving reliability as a system by solving the problem that downloading takes long time to limit service operation when a large number of clients are conventionally connected, efficiently and surely downloading a new program even to a plurality of client without disturbing information distribution service and surely shifting to the new program in a short time on a program change-over day.

In this program distributing method, a client 3 acquires new version information from a server 2, downloads a new version program when a download start day arrives, and switches the operating program to the downloaded new version program to start the program when the day for switching-over the programs arrives.