Abstract: A data storage device includes a controller; and a nonvolatile memory device comprising a memory region including a plurality of memory cells, the nonvolatile memory device being suitable for acquiring first data by applying a first read voltage to the plurality of memory cells and acquiring second data by applying a plurality of second read voltages to the plurality of memory cells, according to control of the controller, wherein the controller is suitable for performing an error correction operation for the first data, based on the second data, and wherein the plurality of second read voltages have nonlinear variation rates with respect to the first read voltage.