A safety device for detachably locking the output member of a linear drive, comprising: - a coupling rod which can be coupled to the output member of the linear drive, wherein the output member is movable by means of the coupling rod, - a housing through which the coupling rod passes in a linearly displaceable manner, - a blocking unit through which the coupling rod passes in a linearly displaceable manner and which is movable, relative to the housing, between a blocking position which blocks a stroke of the coupling rod and a release position which allows a linear movement of the coupling rod, - a spring means for preloading the blocking unit into the blocking position, - a locking means for locking the blocking unit in the release position, the locking means comprising locking rolling bodies (34a-c) accommodated in the housing and a support sleeve through which the coupling rod passes in a linearly displaceable manner, it being possible to move the support sleeve between a support position, in which the support rolling bodies (34a-c) are held in a latching position radially outwards in latching engagement with the blocking unit, and a disengaged position, in which a retraction of the support rolling bodies (34a-c) radially inwards out of engagement with the blocking unit is made possible, - an electromagnet means which, when energized, holds the support sleeve in the support position against the actuating force of at least one release spring of a release spring means in such a way that, in the event of a power failure, the holding function can be reversed and the support sleeve moves into the disengaged position by means of the at least one release spring, as a result of which the blocking unit can be transferred into the blocking position by means of the spring means; characterized in that a plurality of support rolling body groups are provided which are grouped around the circumference of the support sleeve, each of which has a plurality of support rolling bodies (34a-c) arranged one after the other in the radial direction, wherein a radial extension of the support rolling bodies (34a-c) within a support rolling body group is greater in the locking position of the support sleeve than in the disengaged position of the support sleeve. - a coupling rod which can be coupled to the output member of the linear drive, wherein the output member is movable by means of the coupling rod, - a housing through which the coupling rod passes in a linearly displaceable manner, - a blocking unit through which the coupling rod passes in a linearly displaceable manner and which is movable, relative to the housing, between a blocking position which blocks a stroke of the coupling rod and a release position which allows a linear movement of the coupling rod, - a spring means for preloading the blocking unit into the blocking position, - a locking means for locking the blocking unit in the release position, the locking means comprising locking rolling bodies (34a-c) accommodated in the housing and a support sleeve through which the coupling rod passes in a linearly displaceable manner, it being possible to move the support sleeve between a support position, in which the support rolling bodies (34a-c) are held in a latching position radially outwards in latching engagement with the blocking unit, and a disengaged position, in which a retraction of the support rolling bodies (34a-c) radially inwards out of engagement with the blocking unit is made possible, - an electromagnet means which, when energized, holds the support sleeve in the support position against the actuating force of at least one release spring of a release spring means in such a way that, in the event of a power failure, the holding function can be reversed and the support sleeve moves into the disengaged position by means of the at least one release spring, as a result of which the blocking unit can be transferred into the blocking position by means of the spring means;