To provide a nonvolatile memory device and a method of writing data for reducing the time for changing write voltage to increase speed.

Write operation for writing data by applying write voltage to a memory cell MC through a word line WL or a bit line BL and verify-operation for verifying a write state of the memory cell MC are repeated while increasing write voltage. One power source circuit PW of a plurality of power source circuits PW1-PWN is sequentially selected. The voltage generated by the selected power source circuit PW is used as write voltage.