Second display means front parts, each including an immersion liquid surface level display for a coating liquid for moisture prevention and a lead-free display mark, are formed respectively in upper portions on a left side and a right side that are opposite sides having the one side interposed therebetween. A first display means front part including a board management document number, which defines a material for solder, is formed in a lower portion of the printed circuit board. A lead-free display mark (PBF) is not buried in or mixed with a large number of circuit information displays in the board, and a detailed management number is described in a reduced size to conserve space. Thus, the important lead-free display mark can be displayed with large character marks that also serve to manage a liquid surface.