To provide a method for facilitating the oblique cutting of a metal plate.

In a metal plate cutting device where a supply section A having nipping feed rollers 4A, 4B, a cutting section B having an upper and a lower cutting rotary edge 20A, 20B and an exhaust section C having a nipping exhaust roller are arranged on one straight line, rotary faces of the upper and lower cutting rotary edges 20A, 20B are inclined openedly at an inclination angle for cutting the metal plate to an advancing direction of the metal plate, and the advancing metal plate is cut with a movement at a constant speed in the lateral direction of the metal plate as the rotary edges 20A, 20B are fixedly kept in their positional relation.