The present invention relates to an operation method of a memory system including a nonvolatile memory apparatus having memory cells connected to a plurality of word lines. The operation method comprises the following steps: precharging a word line selected among the word lines; sensing a change in voltage or current of the selected word line after the selected word line is floated; generating information on a progressive error depending on the sensed change in voltage or current; and determining the state of the selected word line or a memory block including the selected word line according to the information on the progressive error.
