Provided is a tunable external cavity laser diode using a variable optical deflector wherein the variable optical deflector, in which a refractive index varies according to an electrical signal, is arranged in a triangular shape between a concave diffraction grating and a reflective mirror. Since a resonant frequency is changed using the electrical signal rather than the mechanical movement, the stable operation and continuous high-speed tenability may be enabled. In addition, when the tunable external cavity laser diode according to the present invention is implemented in an InP/InGaAsP/InP slab waveguide, a variable time determined by the carrier lifetime may be reduced to several nanoseconds or less, the miniaturization is enabled, and the manufacturing costs are significantly reduced due to the process simplification. Moreover, when the concave diffraction grating is designed based on a silica (or polymer) based slab waveguide, the fabrication may be performed even by a lithography process having low resolution, thereby enhancing reproducibility and uniformity of the diffraction grating, and accordingly reducing the manufacturing costs.