To provide an optical signal amplification device which performs a negative feedback optical amplification of a semiconductor optical amplifier by feeding back a surrounding light. In the optical signal amplification device, a connecting structure between the semiconductor optical amplifier and an optical fiber for transmitting the output light of the semiconductor optical amplifier can be made simple and small by using a fiber bragg grating device. A first fiber bragg grating device (FGD1) is provided at an output side of a first semiconductor optical amplifier (16).; When a first input signal light (L1) of a first wavelength (?1) is inputted in the first semiconductor optical amplifier (16), a light (Ls1) excluding the light of the first wavelength (?1) is reflected from the first fiber bragg grating device (FGD1) and it is directly inputted to the first semiconductor optical amplifier (16) again. Therefore, the connecting structure between the first semiconductor optical amplifier (16) and the first fiber bragg grating device (FGD1) for transmitting the output light (Lout) of the first semiconductor optical amplifier (16) can be made simple and small and a high speed response can be achieved.