A stamp unit 1 comprises a holder 4 which is to be set in a holder storage part 70 of a stamp manufacturing device for making a stamping surface on a stamp material 3 held in the holder 4. When the holder 4 is set in the storage part 70, the cam effect is generated between the positioning projection 77 of a fixing member 71 and a slant recess 43 of the holder 4, thereby positioning the holder 4 to a predetermined stamp making position in the storage part 70. In a state where the holder 4 is positioned in place, microswitches 75A and others disposed near the projection 77 of the storage part 70 are selectively turned on and off by cooperation between detection recesses 44 and a peripheral wall 38 of the holder 4, so that the existence and the type (size) of the holder 4 are detected.