PURPOSE: To reduce wrong determination in determining polarity according to an indication on a product by making a polarity indicating part, which is stamped on the surface of an external face of an electronic part, as a collection of minute printings.

CONSTITUTION: After a molded exterior is made with an epoxy resin, a marking printing plate 5 provided with projections and recesses having one side 0.1mm (0.01mm2) is used for the surface of the exterior, that is, a polarity indicating part 1 so that a stamped mode of staggered check can be maintained. The upper part of a product is stamped according to the roller transcription process. When the size of an annodic indicating projection is under 0.0025mm2, a recess becomes shallow close to a condition of virtually no projections and recesses. Also, when it exceeds 0.1mm2, an area of a flat part of the projection is large enough to approach conventional examples, thus diminishing the effect. From these considerations, it is desirable for the size of the anode-indicating projection to be within a range from 0.0025 to 0.1mm2 in area. This enables stamping dispersion to lessen and wrong determination of polarity to reduce.