To provide a plate material inverting device capable of conveying a plate material, which faces upward in a back face thereof, by inverting it, and conveying a plate material, which faces upward in a face thereof, without inverting it, and capable of automatically inverting for conveyance without manual operation by a worker.

This plate material inverting device comprises a conveying means 2 for conveying a plate material 1 along the cross direction thereof, a face and back face determining means 3 for determining a face and a back face of the plate material 1 conveyed by the conveying means 2, a plate material holding means 4 for holding the plate material 1, which is conveyed by the conveying means 2, within a predetermined conveyance range, an inverting means 6 for inverting at least a plate material holding portion 5 of the plate material holding means 4 at 180, and a retreating means 8 for retreating the plate material 1, which is determined that the face thereof faces upward by the face and back face determining means 3, from a plate material holding position 7 by the plate material holding means 4.