The plug-in coupling for connecting a first with a second double-walled, vacuum-insulated cryogenic line (303, 304), which in each case have a media-conducting inner pipe (307, 336), wherein the plug-in coupling comprises a coupling plug and a coupling socket, - wherein the coupling plug has an inner and an outer pipe section (318, 317) as well as a first connecting flange and is connected to the first cryogenic line, - wherein the coupling socket has an inner and an outer pipe section (333, 330) as well as a second connecting flange and is connected to the second cryogenic line, - wherein the outer pipe section of the coupling socket is welded onto the second connecting flange and the end of the outer pipe section remote from the connecting flange is connected in a vacuum-tight manner to one end of the inner pipe section of the coupling socket by means of a connecting ring, - wherein between the inner and the outer pipe section (333, 330) of the coupling socket an annular gap open in the area of the second connecting flange is formed, which is surrounded both on its inner circumference as well as its outer circumference by an insulating vacuum (338, 341), characterized in that the other end of the inner pipe section is welded onto a seal holder, that the media-conducting inner pipe of the second cryogenic line is welded onto the seal holder and that the seal holder carries a seal, which is in contact with the coupling plug in the assembled state of the plug-in coupling and seals the media-conducting inner pipe (307, 336) of the first or second cryogenic line (303, 304). - wherein the coupling plug has an inner and an outer pipe section (318, 317) as well as a first connecting flange and is connected to the first cryogenic line, - wherein the coupling socket has an inner and an outer pipe section (333, 330) as well as a second connecting flange and is connected to the second cryogenic line, - wherein the outer pipe section of the coupling socket is welded onto the second connecting flange and the end of the outer pipe section remote from the connecting flange is connected in a vacuum-tight manner to one end of the inner pipe section of the coupling socket by means of a connecting ring, - wherein between the inner and the outer pipe section (333, 330) of the coupling socket an annular gap open in the area of the second connecting flange is formed, which is surrounded both on its inner circumference as well as its outer circumference by an insulating vacuum (338, 341), characterized in that the other end of the inner pipe section is welded onto a seal holder, that the media-conducting inner pipe of the second cryogenic line is welded onto the seal holder and that the seal holder carries a seal, which is in contact with the coupling plug in the assembled state of the plug-in coupling and seals the media-conducting inner pipe (307, 336) of the first or second cryogenic line (303, 304). the other end of the inner pipe section is welded onto a seal holder, that the media-conducting inner pipe of the second cryogenic line is welded onto the seal holder and that the seal holder carries a seal, which is in contact with the coupling plug in the assembled state of the plug-in coupling and seals the media-conducting inner pipe (307, 336) of the first or second cryogenic line (303, 304).