A semiconductor chip includes a first cell row constituted by I/O cells arranged in the X direction and a second cell row constituted by I/O cells arranged in the first direction, spaced from the first cell row by a predetermined distance in the Y direction. A plurality of external connecting pads include pads each connected with any of the I/O cells and a reinforcing power supply pad that is not connected with any of the I/O cells and is connected with a pad for power supply. The reinforcing power supply pad is placed to lie in a region between the first cell row and the second cell row.