Device for opening a sliding door, in particular a thermally insulating sliding door for cold rooms, the device comprising: an outer handle; an inner handle; a shaft arranged to be insertable into a through hole of a door leaf of the sliding door, coaxially thereto, wherein said through hole extends with its axis (x) perpendicular to an outer side and to an inner side of the door leaf, and wherein the outer handle and the inner handle are arranged to be releasably attached (24, 28) to the opposite ends of the shaft so as to be drivingly connected with each other for rotation about said axis (x), as well as for translation along said axis (x); a bush-shaped inner support element arranged to be insertable over at least a portion of its length into the through hole of the door leaf, coaxially thereto, and to support the shaft for rotation about said axis (x); a mounting plate arranged to be mountable onto the inner side of the door leaf, the inner support element being adapted to be releasably attached to the mounting plate and, through the latter, to the door leaf; an outer support element arranged to support, along with the inner support element, the shaft for rotation about said axis (x), the outer support element comprising a head portion and a stem portion, which in the assembled condition of the device arc arranged respectively outside the door leaf and in the through hole of the door leaf, coaxially to said through hole; and guide means (54, 56) arranged to bring about, as a result of the rotation of the shaft about said axis (x), a simultaneous translation of the shaft along said axis (x); the device being characterized in that the outer support element has a plurality of axial threaded holes, and in that it further comprises a corresponding plurality of tie-rods, each having a head and a threaded shaft, said tie-rods being configured to be inserted each into a respective through hole of the mounting plate, until the respective head is in abutment against the mounting plate, and to be screwed each in a respective hole of said plurality of axial threaded holes of the outer support element so as to bring the head portion of the outer support element into abutment against the outer side of the door leaf. an outer handle; an inner handle; a shaft arranged to be insertable into a through hole of a door leaf of the sliding door, coaxially thereto, wherein said through hole extends with its axis (x) perpendicular to an outer side and to an inner side of the door leaf, and wherein the outer handle and the inner handle are arranged to be releasably attached (24, 28) to the opposite ends of the shaft so as to be drivingly connected with each other for rotation about said axis (x), as well as for translation along said axis (x); a bush-shaped inner support element arranged to be insertable over at least a portion of its length into the through hole of the door leaf, coaxially thereto, and to support the shaft for rotation about said axis (x); a mounting plate arranged to be mountable onto the inner side of the door leaf, the inner support element being adapted to be releasably attached to the mounting plate and, through the latter, to the door leaf; an outer support element arranged to support, along with the inner support element, the shaft for rotation about said axis (x), the outer support element comprising a head portion and a stem portion, which in the assembled condition of the device arc arranged respectively outside the door leaf and in the through hole of the door leaf, coaxially to said through hole; and guide means (54, 56) arranged to bring about, as a result of the rotation of the shaft about said axis (x), a simultaneous translation of the shaft along said axis (x); the device being characterized in that the outer support element has a plurality of axial threaded holes, and in that it further comprises a corresponding plurality of tie-rods, each having a head and a threaded shaft, said tie-rods being configured to be inserted each into a respective through hole of the mounting plate, until the respective head is in abutment against the mounting plate, and to be screwed each in a respective hole of said plurality of axial threaded holes of the outer support element so as to bring the head portion of the outer support element into abutment against the outer side of the door leaf.