In a semiconductor integrated circuit requiring a large number of pads, an internal circuit is arranged in the center portion, and a plurality of two kinds of I/O circuits for inputting and outputting signals from and to the outside and many pads are arranged along four sides of the semiconductor integrated circuit. The plurality of I/O circuits that are of one of the foregoing two kinds are one-pad I/O circuits on which one pad is arranged in a direction toward the internal circuit, whereas the plurality of I/O circuits that are of the other of the foregoing two kinds are two-pad I/O circuits on which two pads are arranged in zigzag relationship in a direction toward the internal circuit. The number of arranged pads equals to the number of pads required for the semiconductor integrated circuit. The one-pad I/O circuits and the two-pad I/O circuits are provided with power source wirings for supplying power thereto. The power source wirings extend along the arrangement direction of the one-pad I/O circuits and the second-pad I/O circuits to be ring-shaped. power source wiring migration areas for changing power source wirings between the one-pad I/O circuits and second-pad I/O circuits are disposed in four corner portions of the semiconductor integrated circuit.