To provide a ceiling board having a metal ceiling binding plate 4 half-rotating and turned into a vertical wall state by the gravity of a roof load in a collapse of a wooden house.

The half-rotating metal ceiling board is so formed that one end of the metal ceiling board binding plate 4 is attached to the side of a wooden-structure room 1 in the upper part of a steel-structure room 2 by hinges with the wooden-structure room 1 and the steel-structure room 2 adjoining to each other, and one end is erected to the wooden-structure ceiling board receiver 6 of the wooden-structure room 1 together with the wooden ceiling board 7.