A pilot-controlled electromagnetic valve system has an electromagnetic valve block mounted on the top of a manifold block. A bearing surface is formed on the top of the electromagnetic valve block at a position adjacent to a screw accommodating recess formed on a joint surface at a side of the electromagnetic valve block. A washer engagement groove is formed at the bearing surface. An inwardly sloped washer having an engagement portion at the inner side thereof is fitted on a screw. The engagement portion is engaged with a side wall of the washer engagement groove. Thus, the electromagnetic valve block is surely secured to the manifold block with the screw even if the electromagnetic valve block is one at an end of a series of electromagnetic valve blocks constituting a valve manifold, or provided singly.