An erase method of a nonvolatile memory includes supplying an erase voltage to a substrate, supplying a selection word line voltage to word lines connected with a selected sub-block within a memory block of the nonvolatile memory, supplying a non-selection word line voltage to word lines connected with an unselected sub-block within the memory block during a first delay time from a point of time when the erase voltage is supplied, and thereafter floating the word lines connected with the unselected sub-block.