On an IC chip, a first ground wiring line and a second ground wiring line that extends from a connection site with the first ground wiring line are disposed in a doubled manner. Among EPROMs storing identical data, the source of a first EPROM is connected to the second ground wiring line and the source of a second EPROM is connected to the first ground wiring line. The drains of the EPROMs are electrically connected to a write voltage line. An OR circuit outputs as 1-bit data of the memory circuit, the logical sum of the data stored by at least two of the EPROMs storing identical data. The EPROMs and the OR circuit are disposed near each other on the IC chip.