The present disclosure relates to a case molding including: a plastic case having an accommodation chamber formed by four sides and a bottom to accommodate the capacitor module, and having an open side on the top for filling a molding agent; a capacitor module including a capacitor device, a first busbar electrically connected with a thermally-sprayed surface of the capacitor device, a second busbar electrically connected with the other thermally-sprayed surface of the capacitor, and an insulating sheet disposed between the first busbar and the second busbar; a filler permeating in a gel or fluid state into the space between the capacitor module and inner walls of the plastic case, and then hardened therein; and a horizontal plate part positioned over the capacitor module and the filler, and has a horizontal plate integrated thereto with the bottom pressing the filler.