To provide an electrolytic apparatus and a method therefor for uniformly performing surface treatment to a workpiece having a plurality of rugged parts at the inside of a hollow part.

The electrolytic apparatus for a workpiece comprises a hollow part communicated to the upper and lower parts of an irregular cross-sectional shape having a plurality of recessed parts at the inside. The electrolytic apparatus comprises: a mounting part for clogging the opening part at the lower part of the workpiece; a pressing part for clogging the opening part at the upper part of the workpiece; and an electrode for being disposed at the inside of the workpiece. The electrode has a hollow cross-sectional shape and has a plurality of jet ports for jetting an electrolyte toward each recessed part of the workpiece, and the mounting part or/and the pressing part have a plurality of water exhaust ports arranged correspondingly to each recessed part of the workpiece.