A ladder resistor includes a first resistor group including a number of resistors connected in series and generating a number of reference voltages, and a second resistor group including a same number of resistors connected in series as the plurality of resistors included in the first resistor group, and generating a number of reference voltages. The plurality of resistors included in the second resistor group corresponds to the plurality of resistors included in the first resistor group, respectively. Each of the plurality of resistors included in the first resistor group and a corresponding one of the plurality of resistors included in the second resistor group, that is, each resistor pair is symmetric with respect to a given point. The first resistor group is separated from the second resistor group so that they face each other with the point between.