PURPOSE: To enable uniform and accurate etching by suspensively dispersing conductive fine particles into an electrolyte in the dissolution chamber so as to electrically conduct a semiconductor member to a work electrode with these conductive fine particles, thereby making the whole surface to be etched have substantailly a same potential.

CONSTITUTION: A Si wafer 3 consists of a P-type layer and an N-type layer so that the side to be etched is the n-type layer, the P-type layer portion is of a more negative potential than the N-type layer portion, and plane-anisotropic etching is proceeded by an electolyte mainly composed of a hydrazine solution. An electrolyte 15 composed of a 100% hydrazine hydrate solution containing several percnets of KCl is introduced into an etching bath 1, and into dissolution chamber 4, conductive fine particles 16 are suspensively dispersed. When a pump 7 is started up after the solution has been prepared, the conductive fine particles 16 fluidly move along with the electrolyte 15 between a work electrode 8 and a Si wafer 3 and are uniformly contacted with the two. When a required voltage is applied from a DC power supply 11, the conductive fine particles 16 are uniformly contacted with the surface of the Si wafer 3 to be etched and the whole surface to be etched is provided with substantially a same potential, so that the etching surface of each chip contained in the Si wafer 3 undergos uniform and accurate etching.