Provided is a monolithic integrated semiconductor broad band light source. In the monolithic integrated semiconductor broad band light source, an electro absorption modulator, a semiconductor optical amplifier, and a light emitting diode are integrated on an InP substrate. Ions are implanted among the electro absorption modulator, the semiconductor optical amplifier, and the light emitting diode to electrically insulate the electro absorption modulator, the semiconductor optical amplifier, and the light emitting diode from one another. Electrodes independently implant currents into the electro absorption modulator, the semiconductor optical amplifier, and the light emitting diode. In particular, it is important to form a current intercepting layer and electrically insulate electrodes from one another but optically connect the electrodes in terms of performance of the monolithic integrated semiconductor broad band light source. The semiconductor optical amplifier and the light emitting diode are integrated into an active layer. As a result, broad band light generated from the light emitting diode is amplified by the semiconductor optical amplifier and modulated by a modulator so as to fabricate a monolithic broad band light source.