To provide an imaging lens which offers a wide angle of view, good distortion aberration correction, and reduced size.

An imaging optical system of the present invention comprises a first optical system which has positive refractive power and makes an expansion side imaging plane conjugate with an intermediate image, and a second optical system which has positive refractive power and makes the intermediate image conjugate with a reduction side imaging plane. A focal length fF of the first optical system and a focal length fR of the second optical system satisfy 0<fF/fR<0.8, and a most expansion-side lens of the second optical system is a negative lens.