To prevent deterioration in the optical performance with the temperature and to reduce restriction for molding in a reflective optical element having a plurality of reflective curved faces adjacently arranged.

The reflective optical element has a base member B1 having a continuous curved face and a resin layer A1 formed from a resin (thermosetting resin or UV-curing resin) as integrated on the curved face of the base member and having a plurality of curved faces discontinuous to one another to form reflective faces R1 to R3 on the surface of the layer. In the optical element, the base member is formed from a material (glass, metals, ceramics or the like) having a smaller coefficient of linear expansion than the resin which forms the above resin layer.