PROBLEM TO BE SOLVED: To provide an inorganic fibrous ceiling board hard to make the dew condensation inside an inorganic fibrous board and capable of maintaining sound absorption efficiency and heat insulating efficiency even when the inorganic fibrous ceiling board is constructed in such a structure as the indoor side becomes high temperature and high humidity. SOLUTION: A waterproofing film 2 having over 50m .hr.mmHg/g of vapor resistance is stuck on the surface placed to the indoor side of an inorganic fibrous board 1 with an adhesive 3. The surface placed on an attic space side of the inorganic fibrous board 1 is covered with a waterproofing film 4 having vapor resistance less than 1/5 of vapor resistance of the waterproofing film 2. The waterproofing film 2 on the indoor side and waterproofing film 4 on the attic space side are connected at those circumferential edge sections, and the circumference of the inorganic fibrous board 1 is completely covered to constitute a ceiling board.