A temperature controller of a plasma processing apparatus, a temperature measurer for a plasma processing apparatus, and a plasma processing apparatus, the temperature controller including a movable cooling plate configured to selectively contact a dielectric window in a plasma chamber, the cooling plate having at least one cooling groove through which a cooling agent for cooling the dielectric window is flowable; at least one cooling port including a cooling passageway that is connected to the at least one cooling groove; and a resilient member configured to resiliently press the cooling port toward the cooling plate such that the cooling plate is relatively movable with respect to the dielectric window.