An optical module in which the light outputted from the light source is condensed before outputted, and yet capable of reducing the development of contaminants on the light condensing area. The optical module includes: a light source for outputting light in the short wavelength region; a transparent member having a light input face and a light output face; and a condensing optical system for inputting the light outputted from the light source to the input face of the transparent member, and focusing the light on the output face. The transparent member has an alkali metal content (e.g. Na or K) of less than 2.0% by weight, and/or with a light absorption of less than 0.65%/mm for the light outputted from the light source.