An actuator device having an expansion unit, which has a magnetic shape memory alloy material (MSM), is configured to interact with a preferably non-magnetic ram unit and executes an expansion movement in an actuating direction as a reaction to an introduced magnetic flow, the expansion unit being oriented towards the ram unit along a longitudinal axis defined by the expansion direction, and being intended to exert an actuating force on said ram unit, wherein the ram unit is guided on the casing side in an associated housing section of the actuator unit, wherein an end section of the expansion unit and/or end section of the ram unit, the end section being realized in a transition region between the expansion unit and the ram unit, is configured such that, at least during the exertion of the actuating force along the longitudinal axis, an overlap that effects a form- and/or force-fit transversely to the longitudinal axis arises in the transition region.