To rationalize the preventive maintenance of a plant or equipment and facilities.

This maintenance supporting method for supporting the maintenance of equipment and facilities, the maintenance scheduled period of equipment and facilities is updated by using a loss function L(t) defined for each equipment facility, and a loss function L(t0) changing with time is calculated based on the information of the equipment and facilities changing with time acquired by remotely monitoring the equipment and facilities, and at least either the optimal check interval or optimal conservation limit is calculated based on the calculated loss function, and the maintenance scheduled time t2 of the equipment and facilities is updated based on the calculated optimal check interval or optimal conservation limit.