Contactless security device, particularly for motorized vertical sliding closing systems, comprising: - at least two opposite security units applicable to an internal face of a motorized door movable along lateral guides for sliding between at least one closed position, wherein a lower side of said motorized door is adjacent to an underlying floor, and at least one open position, wherein said lower side is moved away from said floor, each of said security units comprising: - at least one supporting element fixable to said internal face of the motorized door and provided with at least one guiding slot; and - at least one slider provided with at least one sliding pin, movable along said guiding slot; - optical barrier means, which are adapted to define at least one optical barrier in a first area comprised between said security units and to cause the stop of said motorized door in the presence of an obstacle, said optical barrier means comprising one emitter, associated with one of said sliders, and at least one receiver, associated with the other of said sliders and substantially in line with said emitter, wherein each of said sliders is susceptible of combined horizontal and vertical translation movements to displace said optical barrier between a work configuration, wherein said optical barrier is arranged in parallel below said lower side and on a sliding plane of said motorized door between said open position and said closed position, and a home configuration, wherein said optical barrier is arranged in parallel at a distance from said inner face of the motorized door when the latter is in said closed position; characterized by the fact that said receiver and said emitter are associated with said sliders by interposition of corresponding supporting units rotatable around corresponding axes of rotation, and by the fact that said device comprises at least two security elements which are respectively associated with said supporting units and which extend to second areas comprised between said security units and said lateral guides, in the presence of said obstacle in said second areas, said security elements being adapted to rotate said supporting units, said emitter and said receiver around said axes of rotation and to interrupt said optical barrier. - at least two opposite security units applicable to an internal face of a motorized door movable along lateral guides for sliding between at least one closed position, wherein a lower side of said motorized door is adjacent to an underlying floor, and at least one open position, wherein said lower side is moved away from said floor, each of said security units comprising: - at least one supporting element fixable to said internal face of the motorized door and provided with at least one guiding slot; and - at least one slider provided with at least one sliding pin, movable along said guiding slot; - optical barrier means, which are adapted to define at least one optical barrier in a first area comprised between said security units and to cause the stop of said motorized door in the presence of an obstacle, said optical barrier means comprising one emitter, associated with one of said sliders, and at least one receiver, associated with the other of said sliders and substantially in line with said emitter, wherein each of said sliders is susceptible of combined horizontal and vertical translation movements to displace said optical barrier between a work configuration, wherein said optical barrier is arranged in parallel below said lower side and on a sliding plane of said motorized door between said open position and said closed position, and a home configuration, wherein said optical barrier is arranged in parallel at a distance from said inner face of the motorized door when the latter is in said closed position; characterized by the fact that said receiver and said emitter are associated with said sliders by interposition of corresponding supporting units rotatable around corresponding axes of rotation, and by the fact that said device comprises at least two security elements which are respectively associated with said supporting units and which extend to second areas comprised between said security units and said lateral guides, in the presence of said obstacle in said second areas, said security elements being adapted to rotate said supporting units, said emitter and said receiver around said axes of rotation and to interrupt said optical barrier. - at least one supporting element fixable to said internal face of the motorized door and provided with at least one guiding slot; and - at least one slider provided with at least one sliding pin, movable along said guiding slot; - optical barrier means, which are adapted to define at least one optical barrier in a first area comprised between said security units and to cause the stop of said motorized door in the presence of an obstacle, said optical barrier means comprising one emitter, associated with one of said sliders, and at least one receiver, associated with the other of said sliders and substantially in line with said emitter, wherein each of said sliders is susceptible of combined horizontal and vertical translation movements to displace said optical barrier between a work configuration, wherein said optical barrier is arranged in parallel below said lower side and on a sliding plane of said motorized door between said open position and said closed position, and a home configuration, wherein said optical barrier is arranged in parallel at a distance from said inner face of the motorized door when the latter is in said closed position;