A light quantity measurement unit measures a quantity of light of a light source that has a first light-emitting element that emits light of a first wavelength band and a second light-emitting element that emits light of a second wavelength band. The light quantity measurement unit includes first and second filters having the first and second wavelength bands as the detection wavelength bands. The first and second light-emitting elements are caused to sequentially emit light, and on the basis of the results of measurement of the quantity of light that is measured by way of the first and second filters, a control unit generates first compensation information in which light of the second wavelength band is measured with the first filter and second compensation information in which light of the first wavelength band is measured with the second filter, finds a first compensation light quantity of the first light-emitting element by excluding the quantity of light based on the first compensation information from the quantity of light that is measured by way of the first filter, finds a second compensation light quantity of the second light-emitting element by excluding a quantity of light based on the second compensation information from the quantity of light measured by way of the second filter, and then controls the quantity of light of the first and second light-emitting elements based on the first and second compensation light quantities.