PURPOSE: To mold a thin fender liner generating no wrinkles, by mounting a preceding clamp consisting of three movable clamps.

CONSTITUTION: In a stamping molding apparatus, the inside of the parts grasped by sheet clampers 2 of a resin sheet 1 are further grasped by a movable preceding clamp consisting of a central clamp 3b and end clamps 3a, 3c in order to prevent that the resin sheet 1 is pulled in at the time of molding. The central clamp 3b is moved to the sheet clamper side while the resin sheet 1 is grasped to hold the position thereof and the end clamps 3a, 3c are respectively rotated to the sheet clamper side around the fulcrums 8a, 8c at central side end parts while grasp the resin sheet to hold the angles thereof and width narrowing quantity is partially altered. Next, an upper mold 4 and a lower mold 5 are matched to press the resin sheet 1. By this constitution, a thin fender liner can be molded without generating wrinkles.