The invention relates to a device for insertion of a cannula of e.g. and infusion set for intermittent or continuous administration of a therapeutical 5 substance, such as e.g. insulin. The insertion device assures that before, during and after insertion the insertion needle is not visible to the patient. The insertion device according to the invention comprises a first insertion part (1) and a second insertion part (2), a cannula holding part (5) provided with a 10 cannula (4), and an injection needle (6) where-the second insertion part (2) is connected to the injection needle (6) and the injection needle (6) is releasably combined with the cannula (4) of the cannula holding part (5), -the first insertion part (1) covers the injection needle (6) in a non-activated 15 position and in an activated position the injection needle (6) projects beyond the first insertion part (1), -at least a part of the second insertion part (2) and the first insertion part (1) can be moved in relation to each other between at least one activated position and at least one non-activated position, 20 wherein the second insertion part (2) exceeds the distal end of the first insertion part (1) when the device is in an activated position.
