A memory controller for performing soft decoding according to a Cell Difference Probability (CDP) calculated based on a cell distribution controls a memory device. The memory controller for controlling the memory device, the memory controller comprising: an error corrector configured to correct an error in read data received from the memory device; a command generator configured to output, in response to failing an error correction operation of the error corrector, a cell distribution detection command for detecting threshold voltage distributions of memory cells included in the memory device; and a read voltage controller configured to determine, based on cell distribution detection data that the memory device provides in response to the cell distribution detection command, a number of read voltages for a read operation to be performed in the memory device and an interval between neighboring ones among the read voltages.