A NOR type flash memory includes a plurality of word lines, a plurality of bit lines, at least one bit line, a plurality of nonvolatile memory cells, a row decoder, a cell selection circuit and a programming load. Each of the plurality of nonvolatile memory cells includes a gate electrode, drain electrode and source electrode and the gate electrode is connected to a corresponding one of the plurality of word lines, the drain electrode is connected to a corresponding one of the plurality of bit lines and the source electrode is connected to the source line. The row decoder selects one of the plurality of word lines at the time of data programming. The cell selection circuit includes a column decoder and column gates and is constructed to simultaneously select one bit line from each of the plurality of groups among the plurality of bit lines. The programming load increases the number of programming bits with the progress of programming when data of plural bits is programmed into a plurality of memory cells simultaneously selected by the cell selection circuit.