A method of fabricating a refractive silicon microlens by using micro-machining technology. The method of fabricating a refractive silicon microlens according to the present invention comprises the steps of forming a boron-doped region on a silicon substrate, and selectively removing regions of the substrate except for the boron-doped region to form a lens comprised of only the boron-doped region. With the method of the present invention, it is possible to fabricate a two-dimensional infrared silicon microlens array. By using such a two-dimensional infrared silicon microlens array in an infrared sensor, the detectivity of the infrared sensor can be increased by 3.4 times, which is the refraction index of silicon. In addition, the two-dimensional infrared silicon microlens array of the present invention can be used with commercial infrared telecommunication devices.