A method of reading a nonvolatile memory device may include, after an nth erase operation is performed, reading dummy cells on which a program operation has been performed based on a first read voltage, where n is an integer greater than zero, counting a number of dummy cells that are read as having a threshold voltage lower than the first read voltage, when the number is a critical value or more, resetting a read voltage, and performing, based on the reset read voltage, a read operation on memory cells that belong to the same memory cell block as the dummy cells and on which a program operation has been performed on the memory cells after the nth erase operation has been performed.