There is disclosed a plasma technique in which a plasma generation technique frequently used in various fields including a semiconductor manufacturing process is used, and generation of plasma instability (high-speed impedance change of a plasma) can efficiently be suppressed and controlled in order to manufacture stable products. In a method of disposing an object in a chamber and generating the plasma to treat the object, the chamber is sealed by a surrounding member so as to have an inner space, at least a part of the member includes a dielectric material, an RF induction coil is disposed outside the dielectric member, and a direct-current electric field is supplied into the inner space by a method of passing a direct current through the RF induction coil or another method, so that the plasma is stabilized.