A lens includes: a substrate that includes a diffraction region where a plurality of protruding strips are coaxially and alternately formed. The diffraction region includes a first diffraction region and a second diffraction region that is located in at least a part of a region different from the first diffraction region. The second diffraction region includes: groove spaces lying between adjacent ones of the protruding strips with one another; and a communication space communicating between adjacent ones of the groove spaces with one another.