A terahertz wave lens concentrates or collimates a terahertz wave. The terahertz wave lens includes a substrate having a surface provided with an uneven structure that changes a phase of the terahertz wave. The uneven structure includes a plurality of pillars that are periodically arranged. The uneven structure includes a plurality of regions where the plurality of pillars are arranged. A height of the pillar in a thickness direction of the substrate and a width of the pillar differ for each of the regions. A distance (period) between centers of the pillars adjacent to each other is constant. Outer end portions of the uneven structure in the thickness direction are located on the same plane.