The invention relates to an injector device for an infusion set for intermittent or continuous administration of a therapeutical substance, such as insulin. The injector device for the subcutaneous introduction of the cannula of an infusion part into the skin of a patient comprises a housing, a back, longitudinally extending guiding means, a member which is longitudinally slidable within the housing, an insertion needle for insertion of the cannula, a spring located between the back of the housing and the longitudinally slidable member, locking means for maintaining the spring in a compressed state and release means for disengaging the locking means. The device further comprises a pivoting member which can be swung from a position in which the pivoting member allows for insertion of the needle into a position in which it embraces the needle.