A production method of an electronic part comprising a step o working a substrate having formed thereon a metal thin-film conductor using water, wherein said water satisfies the relations 3.5≦pH≦6.5 and DO≦0.5 pH2−6.5 pH+22 [wherein DO represents a dissolved oxygen amount (unit ppm)]. By using the water in the case of working substrates in the production steps of electronic parts, the generations of the static electricity and the oxidation caused by water used for working are restrained. The present invention is particularly effective in working of an electronic part wherein a metal thin-film conductor containing at least two kinds of metals including Al on a substrate having a pyroelectric property.