To provide a device for stacking more planar plate materials having protruding machined portions in the direction of their heights even when plate materials different in size are mixed therein.

The device for placing the planar plate materials M having protruding machined portions Ma comprises a placement board member 62 and a placement board member supply device 63. The placement board member 62 can be placed on a plate material placement part 61 while covering the plate materials M placed on the plate material placement part 61 and it has an upper plane 62a on which the plate materials M can be placed. The placement board member 62 has a lower opening 73 and a storage space 74 for storing the plate materials M between the upper plane 62a and itself. The placement board member supply device 63 supplies the placement board member 62 with the upper plane 62a in horizontal.