Disclosed is a foam board of a polyolefin resin, which has an excellent thermal insulation property and an excellent sound absorption property, whose final product can be material-recycled, which is inexpensive, an which can be produced continuously. Also disclosed is a method for producing a foam board, which comprises conducting the extrusion foaming of a mixture of a polyolefin resin composition and a foaming agent by ejecting the mixture under atmosphere through an extruder equipped with a multi-hole-type die at a melt-extrusion temperature of 160 to 250 DEG C, at an ejection amount (V) of0.05 to 0.45 kg/hr per one opening in the die, and at a proximal resin pressure of 7 to 20 MPa at the opening of the die, wherein the polyolefin resin composition comprises a linear polypropylene resin having a melt tension of 5 to 30 g at 230 DEG C, the foaming agent comprises at least carbon dioxide in the supercritical state, and the multi-hole-type die has an opening diameter of 0.1 to 1.0 mmand the number of openings of 50 to 5000.