A gamma voltage generating apparatus operated in various modes comprising: a red gamma voltage generator generating a red gamma voltage; a green gamma voltage generator generating a green gamma voltage; and a blue gamma voltage generator generating a blue gamma voltage, wherein each of the red, green and blue gamma voltage generators (42, 44, 46) is commonly connected to a supply voltage source, wherein the red gamma voltage generator includes a first voltage-dividing resistor connected to the supply voltage source, a first variable resistor connected to the first voltage-dividing resistor, second and third voltage-dividing resistors (R2, R3) connected in parallel between the first variable resistor and a ground voltage source, a first switch connected between the second voltage-dividing resistor and the ground voltage source, and a second switch connected between the third voltage-dividing resistor and the ground voltage source, wherein the green gamma voltage generator includes a 11th voltage-dividing resistor connected to the supply voltage source, a second variable resistor connected to the 11th voltage-dividing resistor, 12th and 13th voltage-dividing resistors (R12, R13) connected in parallel between the second variable resistor and a ground voltage source, a 11th switch connected between the 12th voltage-dividing resistor and the ground voltage source, and a 12th switch connected between the 13th voltage-dividing resistor and the ground voltage source, and wherein the blue gamma voltage generator includes a 21st voltage-dividing resistor connected to the supply voltage source, a third variable resistor connected to the 21st voltage-dividing resistor, 22nd and 23rd voltage-dividing resistors (R22, R23) connected in parallel between the third variable resistor and a ground voltage source, a 21st switch connected between the 22nd voltage-dividing resistor and the ground voltage source, and a 22nd switch connected between the 23rd voltage-dividing resistor and the ground voltage source. a red gamma voltage generator generating a red gamma voltage; a green gamma voltage generator generating a green gamma voltage; and a blue gamma voltage generator generating a blue gamma voltage, wherein each of the red, green and blue gamma voltage generators (42, 44, 46) is commonly connected to a supply voltage source, wherein the red gamma voltage generator includes a first voltage-dividing resistor connected to the supply voltage source, a first variable resistor connected to the first voltage-dividing resistor, second and third voltage-dividing resistors (R2, R3) connected in parallel between the first variable resistor and a ground voltage source, a first switch connected between the second voltage-dividing resistor and the ground voltage source, and a second switch connected between the third voltage-dividing resistor and the ground voltage source, wherein the green gamma voltage generator includes a 11th voltage-dividing resistor connected to the supply voltage source, a second variable resistor connected to the 11th voltage-dividing resistor, 12th and 13th voltage-dividing resistors (R12, R13) connected in parallel between the second variable resistor and a ground voltage source, a 11th switch connected between the 12th voltage-dividing resistor and the ground voltage source, and a 12th switch connected between the 13th voltage-dividing resistor and the ground voltage source, and wherein the blue gamma voltage generator includes a 21st voltage-dividing resistor connected to the supply voltage source, a third variable resistor connected to the 21st voltage-dividing resistor, 22nd and 23rd voltage-dividing resistors (R22, R23) connected in parallel between the third variable resistor and a ground voltage source, a 21st switch connected between the 22nd voltage-dividing resistor and the ground voltage source, and a 22nd switch connected between the 23rd voltage-dividing resistor and the ground voltage source.