An optical element using visible light from wavelengths λS to λL (λL>λS), is formed of a translucent material having refractive indexes nS and nL, respectively, for light having the wavelengths λS and λL. The optical element includes an incident face; an exit face; and a micro convexo-concave structure used as an anti-reflection structure (ARS), being formed at least one of the incident face and the exit face. An average distance P between adjacent micro convexo-concave structures satisfies condition (1) P≦0.8·λS/nS. Dimensionless parameters mS and mL satisfy condition (2) 0.8≦mS≦1.1 and condition (3) 0.8≦mL≦1.1. The parameters mS and mL, an average height H, the wavelengths λS and λL, and the refractive indexes nS and nL of the micro convexo-concave structure satisfy condition (4) mS·λS/(2·nS)≦H≦mL·λL/(2·nL).