To improve a yield and enhance productivity, and adjust a color of mixed light accurately and easily without complicating a circuit configuration of a light emitter even if each of light emitting diodes has a variation in productivity.

First, when a current is applied to each of light emitting diodes 40, 41 and 42 from a fixed current source 5, an optical sensor 2 detects while light. Next, the white light detected by the optical sensor 2 is diffracted, and intensities of red, green and blue lights are detected. Then a comparator 31 inputs the intensities of the red, green and blue lights as detection values from the optical sensor 2, and compares them with a reference value stored in advance in a storage 30. When it is determined that the detection value differs from the referenece value, a setting section 32 sets resistance values of variable resistances 43, 44 and 45 so as to make the resistance values coincide with the reference values.