PURPOSE: To uniformize each film thickness on both sides of a base plate and improve the throughput for polishing.

CONSTITUTION: A base plate holder 7 capable of rotation and revolution is installed in space between a vertical pair of polishing surface plates 1 and 3 standing opposite up and down and rotating in the reverse direction to each other. In addition, each base plate installing hole 8 is installed is this base plate holder 7, while at least more than one holes 9 are installed there in order to feed the lower surface plate 1 with an abrasive 30 being fed to a top surface of the base plate from the polishing upper surface plate 3. With this constitution, a part of the abrasive 30 to be fed to the top surface of the base plate 10 is fed to an interval between a lower surface of the base plate 10 and the lower surface plate 1 through each of the holes 9, whereby it is able to be supplied for polishing the lower surface of the base plate 10. In addition, swarf sludge accumulated on the lower surface plate 1 can be discharged through the holes 9.