To obtain a polyacetylene-contg. molded article which has a protective coating of SinX and hence has an improved stability against air and esp. oxygen.

This molded article, formed from a polymer product contg. polyacetylene and a polymer other than polyacetylene, contains a protective coating of SinX (wherein X is 1-2, pref. 1.1-1.9, esp. pref. 1.4-1.8). The protective coating is formed by physical vapor deposition, plasma chemical vapor deposition, or sputtering and remarkably stabilizes polyacetylene against oxygen even when the layer is very thin, for example, it is 10 nm to 10 μm, pref. 100 nm to 1 μm. Though above-described X of SiOX may be 1-2, it is pref. 1.1-1.9, esp. pref. 1.4-1.8, in terms of stabilization of polyacetylene. For obtaining satisfactory mechanical properties, such as scratch resistance, the value of X of up to 2 is useful.