A method of reading data in a non-volatile memory device based on the logic level of a selection bit of an address, determines an order of reading a first and second bits of data stored in one multi-level memory cell corresponding to the address based on the logic level of the selection bit, and senses and outputs the first and second bits of data according to the determined order of reading. The method of reading data in a non-volatile memory device and the method of inputting and outputting data in a non-volatile memory device may reduce the initial read time by selecting the order of reading the first and second bits of data stored in the multi-level memory cell and reading the data according the order based on the start address.