To obtain a solid acid catalyst having high activity and no corrosiveness.

Silicate having meso pores and containing gallium (solid acid catalyst) is obtained by using 8-30C alkyltrimethylammonium as a template to introduce gallium into crystalline silicate. Gallium may be substituted with a part of silicate or may be supported on silicate. This solid acid catalyst is useful as a Lewis acid catalyst, for example, as an acylating or alkylating reaction catalyst due to Friedel-Crafts reaction.