A nonvolatile memory, such as a write-once memory, includes a memory cell array that has first memory cells and at least one second memory cell. The memory also includes a first writing circuit that is capable of writing data to the first memory cells and the second memory cell, a second writing circuit, and a verify circuit which is capable of confirming whether the data is normally stored in the first memory cells. When the writing of data to one of the first memory cells fails, the second writing circuit is arranged to assign an address of the one of the first memory cells to the second memory cell. The first memory cells and the second memory cell are arranged to irreversibly change their electrical resistance when the data is stored in them. The first memory cells and the second memory cell include an organic compound layer interposed between a pair of electrodes.