PURPOSE: To improve the control precision by setting a time for a forward end of a work to reach a pressure applying position for a counting completion value after detecting the forward end, counting this time and a time required for pressure applying action are counted starting pressure applying simultaneouly as counting these is completed, and releasing the pressure applying when a forward end passes the pressure applying position.

CONSTITUTION: The number of a pulse signal Pa is set for a counting completing value for a counter C1 till a forward end of a work W gets to a position (a position shown with a continuous line) where a pressure is applied by a sanding belt 12 after the forward end is detected by a sensor 14. For a counter C2, a pulse signal number after the back end of the work W is detected by the sensor 14 till pressure applying is released is set. An action time after completion of counting by the counter C1 till pressure applying is completed is set for a timer T1, and a time required till releasing pressure applying is set for a timer T2 respectively. Pressure applying is thus started as the time passes for the counter C1 and the timer T1. Pressure applying is then released as the counting is completed for the counter C2 and the timer T2.