There are provided a storage device and an operating method thereof. A storage device includes a string including a plurality of memory cells, peripheral circuits for, in a read operation of a selected memory cell, applying a read voltage to a selected word line electrically coupled to the selected memory cell, and selectively applying a first pass voltage and a second pass voltage higher than the first pass voltage to unselected word lines electrically coupled to the other unselected memory cells according to a position of the selected word line, and a controller for controlling the peripheral circuits.