To decide the stable operation current of a memory cell without any dependence on the state of a floating gate, and to stably output data from a sense amplifier circuit according to the writing state of the memory cell based on the operation current of the memory cell in a nonvolatile semiconductor memory.

A sense amplifier circuit is a current mirror circuit which includes first and second mirror transistors constituting a mirror circuit, and includes a detection transistor having its own source electrode connected to the selection gate transistor of a selected memory cell and the drain electrode of the detection transistor as a part of a load circuit connected to the drain electrode of the second mirror transistor. The operation current of the selection gate transistor is smaller than that of the detection transistor, and a current output from the second mirror transistor is decided by the operation current of the selection gate transistor.