Device for plating cylinder block and sealing mechanism therefor

A cylinder block plate processing apparatus in which one end side of an inner peripheral surface of a cylinder of a cylinder block is sealed to circulate a process liquid to perform pre-plating or plating processing of the cylinder inner peripheral surface. The apparatus includes: an apparatus body having a workpiece mount table on which the cylinder block is placed; a workpiece holding tool that is provided on the workpiece mount table so as to be vertically movable; an electrode support member including an electrode cylinder mounted to the apparatus body; a processing solution supply member that supplies a processing solution to the electrode support member; an electrode operated by the electrode cylinder; a sealing jig provided to one end of the electrode; a driving mechanism that drives the sealing jig; and a control circuit that controls operations of the processing solution supply member and the driving mechanism.