Etching method of substrate made of fragile material

The utility model provides an etching method of a substrate made of fragile material. An etching groove can be formed stably when performing cross etching along mutually cross etching predetermined lines. And the grinding and processing of corner parts in following procedures become easy. The etching method is a method etching along the mutually cross etching predetermined lines on the substrate made of the fragile material and includes a first procedure and a second procedure. In the first procedure, a through substrate and through hole provided with a peripheral part extending along the crossed etching predetermined lines are formed at a cross point of the crossed etching predetermined lines. In the second procedure, cracks develop along the etching predetermined lines from the through hole.