A storage device configured to provide an improved data recovery rate includes a memory device including a plurality of memory cells and a memory controller. The memory controller includes a read operation controller for controlling the memory device to perform a read operation by applying a default read voltage or optimal read voltage to a selected word line coupled to selected memory cells among the plurality of memory cells; and an optimal read voltage operating component for determining the optimal read voltage when the read operation using the default read voltage fails, based on an average threshold voltage and cell number information which are information on a memory cell number for each of first and second distributions which are adjacent threshold voltage distributions among threshold voltage distributions that the threshold voltages of the selected memory cells form.