A lighting device comprising: a first and a second switching power supply circuit (10 and 20) which are connected in parallel to an input DC power supply to drive a first semiconductor light emitting element emitting a first light having a first color temperature and a second semiconductor light emitting element emitting a second light having a second color temperature which is different from the first color temperature; a high frequency oscillation circuit (OSC-H) which generates a first and a second high frequency square wave signal serving as on/off switching signals of the first and the second switching power supply circuit (10 and 20), respectively; a low frequency oscillation circuit (OSC-L) which generates a first and a second low frequency square wave signal (PWM1 and PWM2); a first gate circuit (A1 or NOR1) connected to the first switching power supply circuit having a first input to which the first high frequency square wave signal is inputted and a second input to which the first low frequency square wave signal is inputted; and a second gate circuit (A2 or NOR2) connected to the second switching power supply circuit having a first input to which the second high frequency square wave signal is inputted and a second input to which the second low frequency square wave signal is inputted, wherein each of the first and the second low frequency square wave signal (PWM1 and PWM2) has a frequency lower than those of both of the first and the second high frequency square wave signal, and wherein the first low frequency square wave signal determines whether the first high frequency square wave signal is supplied to the first switching power supply circuit, and the second low frequency square wave signal determines whether the second high frequency square wave signal is supplied to the second switching power supply circuit, characterized in that on/off duties of the first and the second low frequency square wave signal (PWM1 and PWM2) are complementarily changed such that a color temperature of a mixed light of the first light and the second light is varied. a first and a second switching power supply circuit (10 and 20) which are connected in parallel to an input DC power supply to drive a first semiconductor light emitting element emitting a first light having a first color temperature and a second semiconductor light emitting element emitting a second light having a second color temperature which is different from the first color temperature; a high frequency oscillation circuit (OSC-H) which generates a first and a second high frequency square wave signal serving as on/off switching signals of the first and the second switching power supply circuit (10 and 20), respectively; a low frequency oscillation circuit (OSC-L) which generates a first and a second low frequency square wave signal (PWM1 and PWM2); a first gate circuit (A1 or NOR1) connected to the first switching power supply circuit having a first input to which the first high frequency square wave signal is inputted and a second input to which the first low frequency square wave signal is inputted; and a second gate circuit (A2 or NOR2) connected to the second switching power supply circuit having a first input to which the second high frequency square wave signal is inputted and a second input to which the second low frequency square wave signal is inputted, wherein each of the first and the second low frequency square wave signal (PWM1 and PWM2) has a frequency lower than those of both of the first and the second high frequency square wave signal, and wherein the first low frequency square wave signal determines whether the first high frequency square wave signal is supplied to the first switching power supply circuit, and the second low frequency square wave signal determines whether the second high frequency square wave signal is supplied to the second switching power supply circuit, characterized in that on/off duties of the first and the second low frequency square wave signal (PWM1 and PWM2) are complementarily changed such that a color temperature of a mixed light of the first light and the second light is varied.