A motion transmission device for gates comprising: - a load-bearing frame having at least one vertical upright adapted to be fixed to a walkable surface; - at least one leaf adapted to be articulated with its vertical upright at the vertical upright of the frame; - a drive unit adapted to be associated with the vertical upright of the frame and equipped with means for transmitting motion to the leaf which are able to rotate the leaf from a closed position of a passage opening to an open position of the passage opening and vice versa; the motion transmission means comprising at least one body having: - a first box-shaped portion which can be associated with the vertical upright of the frame and having at least one through seat and a rotary unit adapted to be housed in the at least one through seat and configured to connect with the drive unit; - a second annular portion configured to form a seat for coupling with a stretch of the vertical upright of the leaf; the second annular portion being equipped with a device for transmitting a rotary movement which can be associated with the stretch of the vertical upright of the leaf; the transmission device being adapted to be connected by a kinematic mechanism of the device with the rotary unit for allowing the passage of the motion from the drive unit to the vertical upright of the leaf, characterised in that the second annular portion comprises a first part and a second part with a curved profile and which can be separated from each other; the first curved part protruding from the first box-shaped portion of the body and the second curved part being associable with the first curved part by means of joining means configured to obtain a mutual stable locking of the first and second parts to define the coupling seat of the stretch of the vertical upright of the leaf positioned before the mutual joining of the first and second curved parts. - a load-bearing frame having at least one vertical upright adapted to be fixed to a walkable surface; - at least one leaf adapted to be articulated with its vertical upright at the vertical upright of the frame; - a drive unit adapted to be associated with the vertical upright of the frame and equipped with means for transmitting motion to the leaf which are able to rotate the leaf from a closed position of a passage opening to an open position of the passage opening and vice versa; the motion transmission means comprising at least one body having: - a first box-shaped portion which can be associated with the vertical upright of the frame and having at least one through seat and a rotary unit adapted to be housed in the at least one through seat and configured to connect with the drive unit; - a second annular portion configured to form a seat for coupling with a stretch of the vertical upright of the leaf; the second annular portion being equipped with a device for transmitting a rotary movement which can be associated with the stretch of the vertical upright of the leaf; the transmission device being adapted to be connected by a kinematic mechanism of the device with the rotary unit for allowing the passage of the motion from the drive unit to the vertical upright of the leaf, characterised in that the second annular portion comprises a first part and a second part with a curved profile and which can be separated from each other; the first curved part protruding from the first box-shaped portion of the body and the second curved part being associable with the first curved part by means of joining means configured to obtain a mutual stable locking of the first and second parts to define the coupling seat of the stretch of the vertical upright of the leaf positioned before the mutual joining of the first and second curved parts.