Tool for removing a glass mounted in an initially airtight watch case by elastic engagement in a recess in the bezel forming a crystal groove, comprising at least the following elements: - a first fitting intended to be positioned on the top of the case in abutment on the external face of the bezel, facing the glass, having substantially the shape of a square-section ring with a cylindrical indentation capable of containing the glass once it has been driven out of the bezel; - a second fitting provided with a thread enabling it to be screwed onto the case in place of a back cover of the watch, and provided, at the centre thereof, with a through-hole to allow compressed air to pass inside the case; - a third fitting having the shape of a solid cylinder intended to be inserted inside the first fitting until it touches the glass; - an axial support part supporting the assembly of the watch case and said fittings (3, 4, 5) comprising a base, a first axial support point supporting said assembly located, when in use, on the case back side and a second axial support point supporting said assembly located, when in use, on the case top side, the first axial support point and the second axial support point being located in the reference axis of the case when in use, the first axial support point being located at the end of a first screw and the second axial support point being located at the end of a second screw, the position of the two screws (13, 14) being adjustable along said reference axis by screwing into the base, the first screw being capable of abutting against the external surface of the third fitting at the first axial support point, the second screw being capable of abutting against the external surface of the second fitting facing the through-hole and being hollow at the centre thereof in order to allow compressed air to pass, the second screw being provided with a head at the part thereof distal from the support, provided with a connector for connecting a flexible hose connected to a pump or for directly connecting a pump; - optionally a flexible hose connected to the pump by a connector; - a pump. - a first fitting intended to be positioned on the top of the case in abutment on the external face of the bezel, facing the glass, having substantially the shape of a square-section ring with a cylindrical indentation capable of containing the glass once it has been driven out of the bezel; - a second fitting provided with a thread enabling it to be screwed onto the case in place of a back cover of the watch, and provided, at the centre thereof, with a through-hole to allow compressed air to pass inside the case; - a third fitting having the shape of a solid cylinder intended to be inserted inside the first fitting until it touches the glass; - an axial support part supporting the assembly of the watch case and said fittings (3, 4, 5) comprising a base, a first axial support point supporting said assembly located, when in use, on the case back side and a second axial support point supporting said assembly located, when in use, on the case top side, the first axial support point and the second axial support point being located in the reference axis of the case when in use, the first axial support point being located at the end of a first screw and the second axial support point being located at the end of a second screw, the position of the two screws (13, 14) being adjustable along said reference axis by screwing into the base, the first screw being capable of abutting against the external surface of the third fitting at the first axial support point, the second screw being capable of abutting against the external surface of the second fitting facing the through-hole and being hollow at the centre thereof in order to allow compressed air to pass, the second screw being provided with a head at the part thereof distal from the support, provided with a connector for connecting a flexible hose connected to a pump or for directly connecting a pump; - optionally a flexible hose connected to the pump by a connector; - a pump.