Memory cells in which an erase and write operation is performed by injecting electrons from a substrate and extracting the electrons into a gate electrode constitute a semiconductor nonvolatile memory device. That is a gate extraction semiconductor nonvolatile memory device. In that device, if an erase bias is applied in a first process of an erase and write operation, memory cells in an overerase condition occur and the charge retention characteristics of such memory cells are degraded. The present invention provides a semiconductor nonvolatile memory device using means for writing all the memory cells in an erase unit before applying the erase bias, and then applying the erase bias.