The disclosure concerns an attaching mechanism for attaching and detaching the inking device of a portable label printing machine, or the like. The attaching mechanism includes a supporting device which is attached to the machine body of the label printing machine. An ink applicator having an inking roller is detachably secured to the supporting device. Stoppers are formed on the supporting device. The stoppers are each comprised of a guide section for guiding emplacing motion of the ink applicator, a stopper section for determining the extent of ink applicator insertion and a retaining section for supporting a portion of the ink applicator and for preventing its leaving the supporting device. The ink applicator is brought into engagement with the supporting device.