There is provided a system and method for monitoring an apparatus from a remote location. A vendor-side computer obtains operating state data obtained by a monitoring device provided in an apparatus via a communication line, and monitors the operating state of the apparatus from a remote location. Maintenance data at a part replacing time is transmitted from the apparatus, and the vendor-side computer that has received maintenance data calculates an optimal replacement period of a part based on this. The calculated optimal replacement period of each part is sent to a plant. The plant feeds the optimal replacement period back to the operating of the apparatus.