A lens having a first surface (1) and a second surface (2). The first surface (1) and the second surface (2) are mirror symmetric to a first symmetric plane (A) passing through an optical axis (Y) of the lens and extend in a first direction (X) perpendicular to the optical axis (Y). The curve profiles of the first surface (1) and the second surface (2) on the cross sections perpendicular to the first direction (X) are configured in such a way that light emitting from a light source (3) arranged at a predetermined position of a second surface side is refracted by the first surface (1) and the second surface (2) to be emitted in a direction which is offset from the optical axis (Y) by more than a predetermined angle.