Provided is an optical component including: a pair of substrate bodies each having a refractive index of not lower than 2 with respect to infrared laser light, and having an incident surface or an emitting surface and an inclined surface inclined with respect to this surface at θi; and an antireflective film which prevents reflection of normal incident infrared laser light, wherein θi is not smaller than a complementary angle θtB of a Brewster's angle θB of infrared laser light incident on a plate member and smaller than a critical angle θc, the inclined surfaces are opposed to each other via a gap, and the incident surface and the emitting surface are arranged in parallel to each other.