A semiconductor storage device equipped with redundant circuits designed to increase the operating speed and to simplify the layout by providing for the detection of the storage of a faulty address and access to the faulty address so as to substitute a spare word line for a faulty word line. The semiconductor storage device includes a MOSFET for causing current to flow through a pair of fuse means by a complementary address signal at one end of a fuse means corresponding to each bit of the faulty address. The other end thereof is connected to a wired OR logic so as to generate a decision signal. The fuse means corresponding to the MOSFET which is turned on by the faulty address signal is cut off to store a faulty address. The faulty address storage and comparison units can be formed with the pair of fuses and the MOSFET. High-speed operation and a high-density layout in the form of a matrix can thus be achieved efficiently by switching the faulty circuit to a spare circuit while the normal decoder is operating.