A reading method of a non-volatile memory device that includes a plurality memory cells that each include one floating gate and two control gates disposed adjacent to the floating gate on two alternate sides of the floating gate, respectively, and two adjacent memory cells share one control gate, the reading method comprising applying a read voltage to control gates of a selected memory cell, applying a second pass voltage to alternate control gates of the memory cells different from the control gates of the selected memory cells starting from the control gates next to the selected memory cell, and applying a first pass voltage that is lower than the second pass voltage to alternate the control gates of the memory cells different from the control gates of the selected memory cells starting from the control gates secondly next to the selected memory cell.