To provide a metal colloidal solution which can give an electrically conductive coating membrane by a mild condition; a method for producing the same; and the electrically conductive coating membrane.

The metal colloidal solution comprises a metal colloidal particle and the polymer of a (thio)phenol derivative having a plurality of repeating units represented by the formula (1), (wherein R1 is hydrogen, a halogen atom, a nitro group, a sulfonate group, an amino group, or an alkyl group substituted optionally with a halogen atom or a hydroxyl group; R2 is hydrogen or a group obtained by removing a halogen atom from an acid halide or an alkyl halide; and X is S, SO, or SO2).