PURPOSE: A substrate block mounting apparatus for a vehicle is provided to tightly fix a substrate block in a mounting space by hanging a mounting hook between spacer projections on a joining sill. CONSTITUTION: A substrate block mounting apparatus for a vehicle comprises spacer projections(26) and mounting hooks(28). The spacer projections are projected from the outer surface of a housing in a pair and are closely adhered to the inner surface of a mounting space. The mounting hook is formed into a cantilever shape at a recessed portion(26') between the pair of spacer projections. The front end of the mounting hook is projected to the upper side of the mounting space. A hanging sill(28') of the mounting hook is hung on a joining sill formed in the inner surface of the mounting space. The bottom edge of the housing is mounted on the hanging sill formed in the inner surface of the mounting space.