A safety device (1) for a previously filled syringe (2) comprising - a hollow support body (1.2) for mounting the previously filled syringe (2) in the, - a hollow needle protection (1.1) that is slidable in relation to the support body (1.2), - and guiding means to relieve the movement of the needle guard (1.1) in relation to the support body (1.2), in which the guiding means comprise - a flexible arm ( 1.1.4) with a guide pin (1.1.3) extending from the flexible arm (1.1.4) in a radial direction, - a guide track (1.2.5), in which the guide pin ( 1.1.3) protrudes to the guide track (1.2.5) and - a separating wall (1.2.6) that extends to the guide track (1.2.5) in a direction parallel to a central axis (A) of the safety device (1) and in which, when the needle guard (1.1) is slid relative to the support body (1.2), the guide pin (1.1.3) moves to the or along the guide track (1.2.5) and the movement of the guide pin (1.1.3) along the guide track (1.2.5) is guided by the interaction of the flexible arm (1.1.4 ) and the separating wall (1.2.6), characterized in that, when the needle guard (1.1) is slid relative to the support body (1.2), the guide pin (1.1.3) moves to along the guide track (1.2.5) to deflect the flexible arm (1.1.4) in a lateral direction (L) perpendicular to the central axis (A) and by which the safety device (1) comprises means (1.2. 1, 1.2.2) to prevent relative rotation between the support body (1.2) and the needle guard (1.1).Un dispositivo de seguridad (1) para una jeringuilla (2) llenada previamente que comprende - un cuerpo de soporte hueco (1.2) para montar la jeringuilla (2) llenada previamente en el, - una protección (1.1) de aguja hueca que es deslizable con relación al cuerpo de soporte (1.2), - y medios de guiado para aliviar el movimiento de la protección (1.1) de aguja con relación al cuerpo de soporte (1.2), en el que los medios de guiado comprenden - un brazo flexible (1.1.4) con una espiga de guiado (1.1.3) que se extiende desde el bra
