A method of controlling a non-volatile memory device includes comparing the number of banks that are in operating states with a threshold value. If the number of the banks is smaller than the threshold value, data stored in a standby bank is read. If there is no bank having data to be read, a standby bank is programmed. If the number of the banks is equal to or greater than the threshold value or if the reading or the programming is performed, it is determined whether there is a reading or programming command to be performed. If there is the reading or programming command to be performed, the process is repeated from the comparing step. The programming may include programming of a most significant bit (MSB) page or a least significant bit (LSB) page.