To prevent polarity errors in mounting an electronic component by making the mark for use in mounting an electronic component different from the mark for use in post-mounting, wherein the mark for confirming the polarity in the mounting is made as large as the size of the electronic component, i.e., much larger than conventional.

An additional mark 41 is provided for use only for manual mounting of an aluminum electrolytic capacitor. The mark 41 is used only in mounting an electrolytic capacitor 50, and is marked by painting whole of a wide area that corresponds to one of the polarities inside the boundary line of an outer dimension drawing 21 which shows position of the electrolytic capacitor 50. In mounting an aluminum electrolytic capacitor 50 onto a printed wiring board 10, the aluminum electrolytic capacitor 50 is mounted on the outer dimension drawing 21, so that a mark 51 on the aluminum electrolytic capacitor 50 showing the polarity is set to the mark 41 on the printed wiring board showing the polarity of the aluminum electrolytic capacitor 50 to be mounted.