To make it possible to easily crush the gypsum lath board body parts and cardboard parts of gypsum lath boards and to separate the gypsum lath board body parts and the cardboard parts.

This treating device 10 for the gypsum lath boards for buildings, and the like, separates the gypsum lath board pieces stuck with the cardboard on one or both surfaces of the planar gypsum lath board bodies to the gypsum lath board body parts and the cardboard parts. In such a case, The device has a receiving section 18 for accepting the fed gypsum lath board pieces and a crushing section 20 connected in communication with the receiving section 18. The crushing section 20 has first and second crushing bodies 49 and 51 which have crushing surfaces 47 on the surfaces and move slidingly relatively to each other in the state of putting the gypsum lath board pieces therebetween. The gypsum lath board body parts and the cardboard may be surely separated by the first and second crushing bodies.