PURPOSE: To form a capillary column groove on the silicon substrate of a gas chromatograph device and to improve accuracy by forming a P type silicon semiconductor layer in the etching region of an N type silicon wafer.

CONSTITUTION: The P type silicon semiconductor layer 9 having a prescribed shape and prescribed size is formed on the specular surface of the silicon wafer 1. A metallic layer 16 is provided on the N type silicon wafer 1, on which the P type silicon semiconductor layer is formed, on the side opposite from the side where the layer 9 is formed. The wafer is then put into an electrolytic cell 13 having a heater 12 and is etched by using an anisotropic etching agent consisting of sodium hydroxide, etc. with said metallic layer as an anode and a platinum plate 14 as a cathode. The P type silicon semiconductor layer having the prescribed shape is allowed to remain on the silicon wafer by the difference in the etching speed between the N type silicon semiconductor layer 1 and the P type silicon semiconductor layer 9 by which the substrate for a column is obtd.