A single-liquid type paint composition comprises: a hydroxyl group-containing polyester resin (A) of which the weight average molecular weight is from 1,500 to 8,000, the acid value is from 0 to 50 mgKOH/g, the hydroxyl group value is from 100 to 180 mgKOH/g and the glass transition temperature is from −30 to 0° C. and a crosslinking agent (B) which reacts with hydroxyl groups, wherein the (A) component has been obtained by reacting a polybasic acid (a), a polyhydric alcohol (b) and at least one type of component (c) having at least six carbon atoms selected from among the saturated mono-carboxylic acids, saturated mono-alcohols, saturated glycidyl ethers and saturated glycidyl esters where the proportion by mass of the (c) component is from 20 to 60 mass % with respect to the sum of the solid fraction masses of the (a) to (c) components.