To provide a lens for the defogging the inside face of a lamp for a vehicle in which a defogging film is formed by plasma polymerization while making the surface of the lens hard to be damaged and also avoiding the increase of its cost as possible.

In the lens for defogging the inside face in a lamp for a vehicle, the inside face 3b of a lens 3 in a lamp for a vehicle is collided with an ionized gas and is subjected to plasma treatment, thus the inside face 3b is activated to form an activated layer; the activated layer is collided with a monomer gas 6, and, by plasma polymerization, a water-repellent plasma polymerized layer 7 is formed; and the plasma polymerized layer 7 is collided with an ionized gas, and is subjected to plasma treatment to form a hydrophilic layer.