An optical wavelength dispersion device and manufacturing method therefor are disclosed, which the optical wavelength dispersion device includes a waveguide unit and a reflector, wherein the waveguide unit has a first substrate, an input unit, a grating and a second substrate. The input unit is formed on the first substrate and having a slit for receiving an optical signal, a grating is formed on the first substrate for producing an output beam once the optical signal is dispersed, the second substrate is located on the input unit and the grating, and forms a waveguide space with the first substrate, the reflector is located outside of the waveguide unit, and is used for change emitting angle of the output beam.