A lighting apparatus, comprising: a switching element connected in series to a DC power supply and controlled to be turned on and off at high frequency; an inductor through which a current flows from the DC power supply when the switching element is turned on, said inductor being connected in series to the switching element; a diode adapted to discharge, when the switching element is turned off, electromagnetic energy stored in the inductor to a light source load comprising a semiconductor light emitting element; an output capacitor connected in parallel with the light source load and adapted to smooth a pulsation component of an output current supplied to the light source load, said pulsation component being caused by the turning on and off of the switching element; and a control circuit adapted to control an On and Off operation of the switching element, wherein the control circuit comprises first, second and third control modes as control modes of the switching element, and is adapted: in the first control mode, to turn the switching element on and off at a predetermined oscillating frequency and an On time so that a current flows through the inductor in a critical mode or a discontinuous mode; in the second control mode, to fix the oscillating frequency of the switching element and change the On time of the switching element, and in the third control mode, to fix the On time of the switching element and change the oscillating frequency of the switching element, wherein the second control mode and the third control mode are allocated for at least two intervals of intervals into which a dimming range between a minimum dimming ratio and a maximum dimming ratio is divided, and wherein the control circuit is adapted: if a full lighting mode is designated, to select the first control mode to fully light the light source load; and if a dimming ratio is designated, to select one of the second and third control modes according to the interval, to which the dimming ratio corresponds, to dim the light source load at the dimming ratio. a switching element connected in series to a DC power supply and controlled to be turned on and off at high frequency; an inductor through which a current flows from the DC power supply when the switching element is turned on, said inductor being connected in series to the switching element; a diode adapted to discharge, when the switching element is turned off, electromagnetic energy stored in the inductor to a light source load comprising a semiconductor light emitting element; an output capacitor connected in parallel with the light source load and adapted to smooth a pulsation component of an output current supplied to the light source load, said pulsation component being caused by the turning on and off of the switching element; and a control circuit adapted to control an On and Off operation of the switching element, wherein the control circuit comprises first, second and third control modes as control modes of the switching element, and is adapted: in the first control mode, to turn the switching element on and off at a predetermined oscillating frequency and an On time so that a current flows through the inductor in a critical mode or a discontinuous mode; in the second control mode, to fix the oscillating frequency of the switching element and change the On time of the switching element, and in the third control mode, to fix the On time of the switching element and change the oscillating frequency of the switching element, in the first control mode, to turn the switching element on and off at a predetermined oscillating frequency and an On time so that a current flows through the inductor in a critical mode or a discontinuous mode; in the second control mode, to fix the oscillating frequency of the switching element and change the On time of the switching element, and in the third control mode, to fix the On time of the switching element and change the oscillating frequency of the switching element, wherein the second control mode and the third control mode are allocated for at least two intervals of intervals into which a dimming range between a minimum dimming ratio and a maximum dimming ratio is divided, and wherein the control circuit is adapted: if a full lighting mode is designated, to select the first control mode to fully light the light source load; and if a dimming ratio is designated, to select one of the second and third control modes according to the interval, to which the dimming ratio corresponds, to dim the light source load at the dimming ratio. if a full lighting mode is designated, to select the first control mode to fully light the light source load; and if a dimming ratio is designated, to select one of the second and third control modes according to the interval, to which the dimming ratio corresponds, to dim the light source load at the dimming ratio.