A device for closing a pipeline, with the latter applied as a branch from a pipe for the transport of fluids, said device (1, 101) being of the type designed to be operated from outside to define an open position and a closed position, to allow or prevent, respectively, the inflow of said fluid towards the above mentioned branching pipeline, the device including: - a box-like body (2, 102), consisting of two half-shells, a lower half-shell (3, 103) and an upper half-shell (4, 104), removably sealed to each other, between which a cavity (5, 105) is defined, which communicates with two openings (31, 131; 41, 141), each of which is realized in the wall of one of said half-shells (3,103; 4, 104), in coaxial relation with each other; - first fastening means, designed to connect said device (1, 101) with the underlying section of said branching pipeline; - second fastening means, designed to connect said device (1, 101) with the overlying section of said branching pipeline; - a shutter (50, 150), slidingly housed in said cavity (5, 105) and movable between two extreme positions, an open position and a closed position, in which said underlying and overlying sections of the branching pipeline are set in communication and separated, respectively; - pinion (80, 180) and rack (81, 181) actuating means (8, 108), adapted to be operated from outside of said box-like body (2, 102) for moving said shutter (50, 150) between the two relative mentioned positions (H, K); the device being characterized in that: said box-like body has, in plan view, a rectangular profile with rounded corners and said opening (31, 41) are situated in central position with respect to the longer sides of the box-like body, with a trapezoidal projection located at the centre of one of said longer sides, said pinion being housed in the region of said trapezoidal projection; said sliding shutter has, in plan view, a rectangular profile with rounded corners and presents a through hole, arranged asymmetrically with respect to the longer sides of said profile, so as to be very close to one of the shorter sides of the latter; the above mentioned rack of said actuating means is made along one of the above mentioned longer sides and the same shutter is moved parallel thereto, upon command imprinted by said pinion meshed with the rack, between the relative above mentioned open and closed positions, in which said through hole is coaxial with and at the side of said openings (31, 41) of the half shells (3, 4), respectively; and seals are provided, interposed between said lower half-shell and the aforementioned sliding shutter (50, 150), respectively, as well as between the latter and the above mentioned upper half-shell (4, 104), designed to surround the openings (31, 131; 41, 141) of the same half-shells (3, 103; 4, 104) and to separate them from said cavity (5, 105). - a box-like body (2, 102), consisting of two half-shells, a lower half-shell (3, 103) and an upper half-shell (4, 104), removably sealed to each other, between which a cavity (5, 105) is defined, which communicates with two openings (31, 131; 41, 141), each of which is realized in the wall of one of said half-shells (3,103; 4, 104), in coaxial relation with each other; - first fastening means, designed to connect said device (1, 101) with the underlying section of said branching pipeline; - second fastening means, designed to connect said device (1, 101) with the overlying section of said branching pipeline; - a shutter (50, 150), slidingly housed in said cavity (5, 105) and movable between two extreme positions, an open position and a closed position, in which said underlying and overlying sections of the branching pipeline are set in communication and separated, respectively; - pinion (80, 180) and rack (81, 181) actuating means (8, 108), adapted to be operated from outside of said box-like body (2, 102) for moving said shutter (50, 150) between the two relative mentioned positions (H, K); said box-like body has, in plan view, a rectangular profile with rounded corners and said opening (31, 41) are situated in central position with respect to the longer sides of the box-like body, with a trapezoidal projection located at the centre of one of said longer sides, said pinion being housed in the region of said trapezoidal projection; said sliding shutter has, in plan view, a rectangular profile with rounded corners and presents a through hole, arranged asymmetrically with respect to the longer sides of said profile, so as to be very close to one of the shorter sides of the latter; the above mentioned rack of said actuating means is made along one of the above mentioned longer sides and the same shutter is moved parallel thereto, upon command imprinted by said pinion meshed with the rack, between the relative above mentioned open and closed positions, in which said through hole is coaxial with and at the side of said openings (31, 41) of the half shells (3, 4), respectively; and seals are provided, interposed between said lower half-shell and the aforementioned sliding shutter (50, 150), respectively, as well as between the latter and the above mentioned upper half-shell (4, 104), designed to surround the openings (31, 131; 41, 141) of the same half-shells (3, 103; 4, 104) and to separate them from said cavity (5, 105).