ETCHING METHOD

PURPOSE:To improve etch factors by incorporatin a process of forming a chemical resistant film by photographic techniques on side etching surfaces at the time of forming said film on non-worked parts and perform etching. CONSTITUTION:The surface of a metal 1 formed with a chemical resistant film 2 by photographic techniques is etched to a permissible limit of rate of side etching. Next, the 2nd, for example, positive type photosensitive chemical resistant film 3 is formed over the entire surface of the metal 1 surface in the same manner as mentioned above, after which the rays R parallel to the thickness direction of the metal 1 are applied and the film is developed, whereby side etching preventive films 4 remained by becoming non-photosensitive and insoluble are formed. Thence, etching is resumed, and before it arrives permissible limit of the rate of side etching, the etching is interrupted. The above-mentioned ethcing operation is repeated until prescribed working depth is obtained. Thereby, an etch factor B/A is made extremely large.