PURPOSE: To finish a molded part quickly and surely and at the same time prevent whitening and cracks from developing by a method wherein a cutter equipped with a filing part is used at the cutting-off of a gate mark.

CONSTITUTION: A transparent or translucent plastic molded part with a gate mark 1 thereon is taken out of a mold and stationarily supported by means of a chucking mechanism 3. A cutter 4 is advanced toward the gate mark of the stationarily supported part 2 vertically or laterally in order to cut off the gate mark. No vibration of the cutter is always necessary during the advance of the cutter 4. Whitening and cracks can be prevented from developing in the molded part, because the molded part is finished by using the chucking mechanism 3 to stationarily support the molded part and the cutter blade and filing part 42 to cut off the gate mark and to file the surface, from which the gate mark is cut off.