The electrostatic chuck is made up of: a chuck main body having electrodes; a chuck plate of a dielectric material and having a rib portion with which a peripheral edge portion of the substrate is capable of coming into surface contact, and a plurality of supporting portions which are vertically disposed at a predetermined distance from one another in an inner space enclosed by the rib portion; and a gas introduction means for introducing a predetermined gas into the inner space. When the substrate is held by the electrostatic chuck which is arranged to attract the substrate by the chuck plate and to form a gas atmosphere by supplying a predetermined gas into the inner space, a current value is monitored by causing an AC current to flow in a capacitance of the chuck plate through an AC power supply, a gas flow amount is monitored by causing the gas to flow through the gas introduction means, and a substrate state is managed based on a variation in at least one of the current value and the gas flow amount to prevent damages to the substrate.