An endoscope apparatus including an endoscope and a light source apparatus, the light source apparatus comprising: a semiconductor light-emitting device (42, 43, 44, 45, 61) that generates illuminating light to be supplied to the endoscope; a cooling device (56, 63, 73, 74) configured to be able to cool the semiconductor light-emitting device (42, 43, 44, 45, 61); a semiconductor light-emitting device drive section that supplies, to the semiconductor light-emitting device (42, 43, 44, 45, 61), a semiconductor light-emitting device drive signal for driving the semiconductor light-emitting device (42, 43, 44, 45, 61) to cause the semiconductor light-emitting device (42, 43, 44, 45, 61) to emit the illuminating light; a cooling device drive section that supplies, to the cooling device (56, 63, 73, 74), a cooling device drive signal for driving the cooling device (56, 63, 73, 74) to cause the cooling device (56, 63, 73, 74) to cool the semiconductor light-emitting device (42, 43, 44, 45, 61); a semiconductor light-emitting device drive control section that sets a duty ratio of the semiconductor light-emitting device drive signal and controls an amount of light emission of the semiconductor light-emitting device (42, 43, 44, 45, 61); a temperature sensor that measures a temperature of the semiconductor light-emitting device (42, 43, 44, 45, 61); and a cooling device drive control section controls the cooling device drive section so as to adjust a signal level of the cooling device drive signal based on a measurement result of the temperature sensor, characterized in that the cooling device drive control section is configured to control the cooling device drive section so as to generate the cooling device drive signal having a same duty ratio as the duty ratio of the semiconductor light-emitting device drive signal set by the semiconductor light-emitting device drive control section and having timing synchronized with the semiconductor light-emitting device drive signal. a semiconductor light-emitting device (42, 43, 44, 45, 61) that generates illuminating light to be supplied to the endoscope; a cooling device (56, 63, 73, 74) configured to be able to cool the semiconductor light-emitting device (42, 43, 44, 45, 61); a semiconductor light-emitting device drive section that supplies, to the semiconductor light-emitting device (42, 43, 44, 45, 61), a semiconductor light-emitting device drive signal for driving the semiconductor light-emitting device (42, 43, 44, 45, 61) to cause the semiconductor light-emitting device (42, 43, 44, 45, 61) to emit the illuminating light; a cooling device drive section that supplies, to the cooling device (56, 63, 73, 74), a cooling device drive signal for driving the cooling device (56, 63, 73, 74) to cause the cooling device (56, 63, 73, 74) to cool the semiconductor light-emitting device (42, 43, 44, 45, 61); a semiconductor light-emitting device drive control section that sets a duty ratio of the semiconductor light-emitting device drive signal and controls an amount of light emission of the semiconductor light-emitting device (42, 43, 44, 45, 61); a temperature sensor that measures a temperature of the semiconductor light-emitting device (42, 43, 44, 45, 61); and a cooling device drive control section controls the cooling device drive section so as to adjust a signal level of the cooling device drive signal based on a measurement result of the temperature sensor,