In a light-emitting device according to a first aspect of the present invention, a condenser is configured to smooth an output voltage of a switching power source. A voltage source of the light-emitting device is configured to adjust a voltage of the condenser. A processor of the light-emitting device is configured to turn on a light-emitting element of the light-emitting device. The processor is configured to measure the output voltage in a turning-on period of the light-emitting element and store the measured output voltage on the storage medium as a reference voltage. The processor is configured to turn off the light emitting element. The processor is configured to control a voltage output from the voltage source on the basis of the reference voltage stored on the storage medium so as to adjust the voltage of the condenser immediately before the light-emitting element is next turned on.