PURPOSE: To obtain a refractive index type distribution type lens which can be miniaturized and has the sufficient image forming performance, by irradiating an electromagnetic wave beam which varies its intensity distribution in proportional to a square of the distance from the center axis to a material which varies its refractive index in response to the electromagnetic energy quantity.

CONSTITUTION: A lens material 2 such as the chalcogenide glass, or gerumanium arsenic, etc. is coated in the form of a thin film on a transparent substrate 1. Then an electromagnetic beam 3 which varies its intensity distribution in proportional to a square of the distance from the center axis is irradiated on the material 2. Thus a lens which varies it refractive index in proportional to a square of the distance from the center axis is obtained. As a result, a refractive index distribution type lens which can be miniaturized and has the sufficient image resolving performance can be produced.