There are provided a light polarizing film of a grid type, usable for light at a wavelength in a range of a visible light region to an infrared region, a method of continuously fabricating the same, and a reflective optical film using the light polarizing film. A polypropylene film is passed through rolls 12, a first constant temperature cell 13, and rolls 12' to thereby undergo uniaxial drawing by 4-fold. Thereafter, an aluminum metal is vapor-deposited to a thickness of 100 nm in a vacuum deposition cell 14 to be subsequently passed through rolls 15, a second constant temperature cell 16, and rolls 15', undergoing uniaxial drawing by 2-fold again while partially crystallizing the polypropylene film. At this point in time, the aluminum metal undergoes substantially uniform cracking in a direction orthogonal to a drawing direction. Thereafter, heat treatment is applied to the film in a third constant temperature cell 17, and the film is subsequently taken out by take-up rolls 18. The film-like light polarizing film obtained had a degree of polarization at 99.5%, and light transmittance at 90%, in a region of infrared wavelength in a range of 1 to 10 .mu.m. With two sheets of the films crossed at right angles, reflectance thereof for infrared rays was measured and was found at not less than 99.9%.