An infrared lens 1a includes first to third lenses L1 to L3 which are made of zinc sulfide and arranged in this order from an object side. Each of the first to third lenses L1 to L3 is configured as a positive meniscus lens of which convex surface is opposed to the object. The lenses L1 to L3 are formed by heat-press molding raw powder of zinc sulfide using a lens-shaped mold. In addition, a concave surface (the surface opposed to the image side) of the first lens L1 is formed as a diffractive surface.