A tree wiring distributes an externally supplied clock signal to a plurality of first clock buffers. Routes of the tree wiring are designed so that the externally supplied clock signal can reach the plurality of first clock buffer substantially at the same time. The plurality of first clock buffers are connected to all intersections existing on a mesh wiring in one to one correspondence. The plurality of first clock buffers supply a clock signal supplied thereto through the tree wiring, to the mesh wiring. The mesh wiring protrudes from the intersections thereof which face toward outside by a predetermined length in order to keep load imposed on the plurality of first clock buffers uniform. A plurality of second clock buffers are connected to the mesh wiring, and supply clock signals supplied thereto from the plurality of first clock buffers through the mesh wiring, to a plurality of circuit elements.