A medical light source device includes: a light emitting element； and a processor comprising hardware. The processor is configured to: determine a light source control value； and control the light emitting element to emit light with a light emission amount according to the light source control value by controlling at least one of a supply time of a current and a current value that are supplied to the light emitting element. The processor is further configured to: turn off the light emitting element in the readout period, when the light source control value decreases from a first value to a second value； and turn on the light emitting element in the readout period, when the light source control value increases from a third value, different from the second value, to a fourth value.
