A longitudinal interference fringe pattern projection lens includes: a lens body; a lens first surface that constitutes one surface of the lens body, and that has two convex or concave portions, which extend in parallel to each other in constant direction and have a same shape; and a lens second surface that constitutes the other surface of the lens body, wherein laser light passing through one convex or concave portion interferes with laser light passing through the other convex or concave portion to form a longitudinal interference fringe pattern.