One object of the present invention is to provide a polyolefin resin foam which does not have a difference between the front side and the back side on the top and bottom surfaces which sandwich in the thickness direction the foam which is excellent in flexibility, buffer property, and heat insulation property despite its thinness, and which can be used suitably in the fields of architecture, electricity, electronics, vehicles, and the like as a variety of heat-resistant sealing materials. The surface hardness of the foam measured by a micro rubber hardness tester is 30° or more and 70° or less, and the centerline average roughness Ra75 of a first surface portion on one side of the foam in the thickness direction and of a second surface portion on the other side of the foam in the thickness direction is 5 μm or more and 20 μm or less.