A fixed-focus lens including a first lens group and a second lens group is provided. The first lens group is disposed between a magnified side and a reduced side and includes a first lens and a second lens arranged in sequence from the magnified side to the reduced side. The refractive powers of both the first lens and the second lens are negative, and the first lens is an aspheric lens. The second lens group is disposed between the first lens group and the reduced side and includes a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, and a ninth lens arranged in sequence from the magnified side to the reduced side. The refractive powers of the seven lenses from the third lens to the ninth lens are respectively positive, negative, positive, negative, positive, negative, and positive in sequence.