Provided is a doped tin oxide that can be used as a chemical plating promoter in a method for selectively metallizing a surface of an insulating substrate. Also provided are a polymer composition that includes the doped tin oxide, a polymer molded body, an ink composition, and a method for selectively metallizing a surface of an insulating substrate. The doped tin oxide has a light color, and does not interfere with the color of the substrate while presetting thereof. The doped tin oxide has a strong ability of promoting chemical plating. Using the disclosed doped tin oxide as a chemical plating promoter, a continuous metal layer can be formed with a high plating speed, together with enhanced adhesivity between the metal layer and the insulating substrate.