A de-chuck control method is provided for de-chucking a workpiece from an electrostatic chuck, which includes a chuck electrode and electrostatically attracts the workpiece. The de-chuck control method includes acquiring a time-integration value of a current by measuring the current flowing from the chuck electrode for a predetermined time period after a plasma process is ended and a voltage applied to the chuck electrode is turned off; calculating a difference between the time-integration value of the current and an electric charge charged to the chuck electrode during the plasma process; calculating a counter voltage according to a residual charge of the electrostatic chuck based on the difference and a predetermined correlation between the time-integration value of the current and a torque acting on a support pin for supporting the workpiece; and applying the counter voltage to the chuck electrode while introducing gas into a processing chamber and generating plasma.