A fixed-focus lens adapted to be disposed between a primary image side and a second image side is provided. The fixed-focus lens includes a second lens group, a first lens group, and a curved reflector arranged in sequence from the primary image side to the second image side. The second lens group includes a first lens, a second lens, and a third lens arranged in sequence from the primary image side to the second image side. The first lens and the third lens have positive refractive powers and each of the first lens, the second lens, and the third lens is a spherical lens.