An actuator for an electromagnetically adjustable valve having a drive unit which moves an adjustment element in at least one direction. The adjustment element is divided into at least two assemblies and includes a stroke setting that can be adjusted with respect to a defined operating position, within an adjustment process. The actuator has a reference plane on which a stop can be attached as a setting device. One assembly of the adjustment element enters into operative connection with the stop during the assembly process, and the other assembly of the adjustment element is held in a defined operating position by a positioning device. The two assemblies of the adjustment element can be connected using a securing device which is effective in at least one direction.