According to one embodiment, a plate material cutting method prepares a plate material including a joining member that joins a main body portion to a throw-out portion, sets the plate material on a die including an opening section, and pushes a punch against the joining member. The punch includes a first end portion corresponding to a first end of the joining member which is connected to the main body portion. The punch also includes a second end portion corresponding to a second end of the joining member which is connected to the throw-out portion. A gap smaller than thickness of the plate material is defined between the first end portion of the punch and an inner surface of the opening section. A gap larger than the thickness of the plate material is defined between the second end portion of the punch and the inner surface of the opening section. |