PURPOSE: To enable the simultaneous formation of a large number of through holes with excellent positional accuracy in a short time, by forming a resist layer of a prescribed pattern on both surfaces of a aluminum nitride ceramic substrate, and by immersing this substrate in an etchant to form the through holes corresponding to the pattern of the resist layer in the aluminum nitride ceramic substrate.

CONSTITUTION: A photoresist is applied on both surfaces of an aluminum nitride ceramic substrate by a spinner and, after drying, it is exposed through a glass mask of a through hole pattern. The substrate thus prepared is immersed for development in an organic alkaline developer to melt and remove the resist in the through hole portions to be formed, and ceramic surfaces are exposed at the same positions on the front and back sides. Next, the aforesaid masking substrate is immersed in an etching solution, and in this state, the etchant is agitated to flow. Etching advances from both ceramic surfaces exposed by the immersion for about two hours, and thus the aluminum nitride ceramic substrate 1 wherein a large number of through holes 2 are formed is manufactured.