The present invention provides an interior material of an operator's cab of a work machine, the interior material comprising at least a structure member and a noise absorption layer, wherein the structure member has at least one rib which is formed on an inside surface of a base portion thereof and comes into intimate contact with an inside surface of an exterior material and a hermetically sealed hollow portion is formed by the rib in intimate contact with the exterior material, and the noise absorption layer is disposed on an outside surface of the structure member. With the interior material, a work environment in the operator's cab of the work machine can be enhanced by effectively suppressing the noise entering from an outside of the operator's cab.