in this embodiment the drum jig 1 is designed and manufactured with a minus tolerance so that the pitch p1 of the positioning pins may be smaller than the pitch p2 of the guide holes h fig3 shows a relation that the drum jig 1 and the metal member 11 have when the distance between the head of the metal member 11 to be plated and the exit point o is l2 i e corresponding to the state in fig1 b in this embodiment as well the positioning pins 6 engage with the respective guide holes h at different positions as shown in fig3 for example in the state shown in fig3 the endmost positioning pin 6 of the drum jig 1 on the exit point o side engages with the guide hole h 4 such that it is in contact with an end portion of the guide hole h 4 on a rear b side the entry point i side as described earlier the drum jig 1 is designed such that the pitch p1 of the positioning pins 6 is several micrometers smaller than the pitch p2 of the guide holes this is a value which ensures that the positioning pin engages with the guide hole h on its end portion on the entry point i side thus as the positioning pins are located closer.