A press plate that includes: a plate shaped press portion that is capable of resilient deformation a first slit that is provided to a first wall portion of a support body with length direction along a first edge portion of the press portion, and that penetrates the first wall portion second slits that are provided to a second wall portions of the support body with length direction along second edge portions of the press portion, and that penetrate the second wall portions and a first corner portion slit that is provided straddling a corner portion between the first wall portion and the second wall portion and penetrating the corner portion, that is connected to the first slit, and that is disposed at a separation to the second slit.
