There, the foaming components of the open-celled rigid polyurethane foam of the present invention contain the polyol component, the isocyanate component, the blowing agent, and other ingredients such as those mentioned above, and the content ratio of the polyol component and isocyanate component in the foaming components is in the range of about 0.55-0.95, preferably in the range of about 0.60-0.8