A polyacetal resin composition containing 100 parts by weight of a polyacetal resin, 0.01 to 5 parts by weight of a colorant selected from inorganic and organic pigments, 0.01 to 3 parts by weight of a polyamide resin having a melting point or softening point of 180° C. or less, or a polyetheresteramide resin, 0.01 to 1 part by weight of an aromatic dihydrazide compound or an aliphatic dihydrazide compound having a solubility of less than 1 g relative to 100 g of water at 20° C., and 0.01 to 1 part by weight of a sterically hindered phenolic compound, or a combination of a hindered amine-based light stabilizer and an ultraviolet absorber, exhibits an excellent thermal stability and is capable of suppressing formaldehyde generation and mechanical strength deterioration.