Precious metal colloid, precious metal fine-particle, composition, and method for producing precious metal fine-particle

To provide a precious metal colloid enabling a production in simply and in low cost, a long-term storage, and a formation of a thin film having a high conductivity, a precious metal fine-particle, a composition including the same, and a method for producing a precious metal fine-particle for forming such precious metal colloid, which is a precious metal colloid in which a protection component protects a precious metal fine-particle selected from gold, silver, platinum, and palladium, a precious metal colloid in which the maximum peak of 13C-NMR spectrum of the protection component separated from the precious metal colloid by ultracentrifugation treatment presents in 160 to 190 ppm other than peaks of a primary carbon and an aromatic carbon, or a precious metal colloid in which peaks of 13C-NMR spectrum present in 20 to 90 ppm and 160 to 190 ppm. A reduction agent, such as a peptide or other amino acid compound and glucosamine, and alkali for supporting a reductivity of the reduction agent are added to a solution dissolving a precious metal containing compound to form the precious metal fine-particle by a reduction reaction of a precious metal ion in the precious metal containing compound.