To obtain a polyurethane resin which can be melted even at a low temperature and has a sufficient adhesion strength, when used as an adhesive, by reacting a high molecular diol, a diisocyanate compound and a specific chain extender.

This polyurethane resin which has a flow-starting temperature of 80 to 150°C and can be thermally molded is obtained by reacting (A) a high molecular diol (for example, a polyester diol obtained from a dicarboxylic acid and a low molecular diol), (B) a diisocyanate compound (for example, 4,4'-diphenylmethane diisocyanate) and (C) a chain extender (preferably having methyl or ethyl group as a side chain, such as 3-methyl-1,5-pentanediol). Therein, 5 to 90 mol.% of the chain extender is a low molecular diol which has at least one side chain and whose main chain has ≤7 carbon atoms.