PURPOSE: To dress a surface plate in a plane grinding device without taking out a carrier.

CONSTITUTION: An upper surface plate 4 is made to go up to the specified height. Next, when an inner gear support frame 2a is made to go up, an outer support ring 20 and a roller 28 cane into contact with an internal gear side end and a sun gear side end of a carrier 3, thereby uplifting this carrier 3. With this constitution, the carrier 3 goes up to the height where it separates from a lower surface plate 5 in keeping an engaged state between a sun gear 1 and an internal gear 2 intact. In succession, a brush existing in a standby position is turned round up to an interval between both these surface plates 4 and 5, having it held between these surface plates, and then it is made contact with their grinding surfaces. Next, with the sun gear 1 left stopped intact, both these surface plates 4, 5 and the brush are all rotated, thereby dressing each of the grinding surfaces of these surface plates 4 and 5 by the brush.