PURPOSE: To simplify the operation while achieving an efficient electrolysis, by interposing an electrolytic liquid between a test sheet and a surface to be inspected to attract a cathode terminal element on the sheet by a magnetic force while an anode terminal is attracted on the test piece.

CONSTITUTION: A unit 15 carries a test sheet 2 on the top of a steel test piece 1 through an electrolytic liquid 16 and arranged a cathode terminal element 13 thereon. The test piece 1 and the element 13 are connected to a power source unit 10 and a flat magnet 6 of the element 13 is attracted to the surface 5 to be inspected of the test piece 1 by its own magnetic force and hold, fix and press the sheet 2 on the surface 5 being inspected. A unit 10 and the cathode terminal 11 are connected to a conductor 14 and the upper end of a support bar 8 of the element 13 and the conductor 14 is connected to the magnet 6. The final end of an anode terminal 12 is composed of a magnet and when the terminal 12 is made to abut on a desired part of the test piece 1, magnetic attraction and electric connection are performed.