An access control device (1) for blocking or opening a passage (2) for persons or vehicles. The access control device comprises one or two blocking bodies (3, 3′), each arranged on a carrier (4, 4′). Each blocking body (3, 3′) comprises a mechanically reversibly deformable element (5, 5′) which, in a first position, is substantially planar and opens the passage (2) and, in a second position, assumes a curved shape which blocks the passage (2). One or both ends of the deformable element (5, 5′) are connected to an actuator (7). A controller controls the deformable element for transferring them first between the first and second positions. When transferring the deformable element from the first to the second position, either the distance between the ends of the respective blocking body is reduced or, when the ends have a constant distance, the length of the blocking body is increased.