A method for assembling insulating glass panes from two or more glass sheets filled with a gas other than air, two plates facing each other, arranged parallel to each other vertically to inclined with adjustable mutual distance, a horizontal conveyor arranged near the lower edge of the plates, a first sealing device and a second sealing device, positioned at the protruding edges of both the plates or near these edges or between the plates and can extend between the horizontal conveyor and a point lying above the horizontal conveyor, and having means for feeding a gas other than air into a chamber, delimited on both the sides by the two plates and by the two sealing devices. For assembling overlong insulating glass panes, the glass sheets, at one of which a frame-like spacer is attached on both the sides, are positioned between the plates an the plates opposite each other.