Braking device, comprising: - a base body associable with the chassis of a towing vehicle; - at least a trailer-brake valve able to adjust the pressure along a control line connectable to the braking system of a trailer and along an additional line operatively connectable to the automatic and/or parking brake of the trailer itself; - first command means associable at least with the parking brake of the towing vehicle and activatable to operate the same; - second command means operatively connected to said trailer-brake valve and activatable to send a working fluid under pressure along said control line and to operate the braking of the trailer; characterized in that it further comprises: - a lever comprising at least a first portion hinged to said body around a first axis of rotation, associated with said first command means and movable between a rest position and at least a braking position in which the first command means themselves are deactivated and activated respectively, there being provided removable locking means of said first portion in said braking position, and at least a second portion, graspable by an operator, hinged to said first portion around a second axis of rotation, associated with said second command means and movable between a rest position and at least a braking position in which said second command means are deactivated and activated, respectively; following the operation of said second portion, the latter and said first portion move to a respective braking position by rotating around their respective axes (X, Y), while following the release of said second portion the latter returns to its rest position and said first portion remains stationary in the braking position due to said locking means; - third command means operatively connected to said trailer-brake valve and operable between an active position, in which they maintain the working fluid under pressure along said additional line to maintain deactivated the automatic and/or parking brake of the trailer, and an inactive position, in which they set to zero the pressure of the working fluid along said additional line so as to activate the automatic and/or parking brake; - first and second activation means (25, 26) each movable between a relative first and a relative second work position, in which they activate and deactivate, respectively said third command means, where said first activation means are moved from the first to the second work position following the displacement of said first portion from the rest position to a braking position, and where manual means are provided operable by an operator to move said second activation means from the second to the first work position. - a base body associable with the chassis of a towing vehicle; - at least a trailer-brake valve able to adjust the pressure along a control line connectable to the braking system of a trailer and along an additional line operatively connectable to the automatic and/or parking brake of the trailer itself; - first command means associable at least with the parking brake of the towing vehicle and activatable to operate the same; - second command means operatively connected to said trailer-brake valve and activatable to send a working fluid under pressure along said control line and to operate the braking of the trailer; - a lever comprising at least a first portion hinged to said body around a first axis of rotation, associated with said first command means and movable between a rest position and at least a braking position in which the first command means themselves are deactivated and activated respectively, there being provided removable locking means of said first portion in said braking position, and at least a second portion, graspable by an operator, hinged to said first portion around a second axis of rotation, associated with said second command means and movable between a rest position and at least a braking position in which said second command means are deactivated and activated, respectively; following the operation of said second portion, the latter and said first portion move to a respective braking position by rotating around their respective axes (X, Y), while following the release of said second portion the latter returns to its rest position and said first portion remains stationary in the braking position due to said locking means; - third command means operatively connected to said trailer-brake valve and operable between an active position, in which they maintain the working fluid under pressure along said additional line to maintain deactivated the automatic and/or parking brake of the trailer, and an inactive position, in which they set to zero the pressure of the working fluid along said additional line so as to activate the automatic and/or parking brake; - first and second activation means (25, 26) each movable between a relative first and a relative second work position, in which they activate and deactivate, respectively said third command means, where said first activation means are moved from the first to the second work position following the displacement of said first portion from the rest position to a braking position, and where manual means are provided operable by an operator to move said second activation means from the second to the first work position.