A polyurethane foam is constituted by using a blowing agent selected from the group consisting of iodofluorohydrocarbons, perfluoroalkenes and hydrogen-containing fluoromorpholine derivatives. These blowing agents have a low thermal conductivity and a short life in the air, and thus impose no or very small load such as ozone layer depletion potential (ODP) and global warming potential (GWP) on the environment. The iodofluorohydrocarbon, in particular, can give an incombustibility and self-extinguishing property to the conventionally used inflammable substance such as cyclopentane or the like, and thus is also advantageous from the viewpoint of safety of the thermal insulating material.