Disclosed herein is a semiconductor integrated circuit including a protected circuit; and a protection element formed on the same semiconductor substrate as the protected circuit and adapted to protect the protected circuit, wherein the protection element includes two diodes having their anodes connected together to form a floating node and two cathodes connected to the protected circuit, the two diodes are formed in a well-in-well structure on the semiconductor substrate, and the well-in-well structure includes a P-type well forming the floating gate, an N-type well which surrounds the surfaces of the P-type well other than that on the front side of the substrate with the deep portion side of the substrate so as to form the cathode of one of the diodes, and a first N-type region formed in the P-type well so as to form the cathode of the other diode.