An optical scanning device includes: a first mirror; a second mirror; two non-waveguide regions; an optical waveguide region; and a first adjusting element. The optical waveguide region propagates light. The optical waveguide region and the two non-waveguide regions include respective first regions in which a common material exists. The optical waveguide region or each of the two non-waveguide regions further includes a second region in which a first material having a refractive index different from a refractive index of the common material exists. The first mirror allows part of the light propagating through the optical waveguide region to be emitted through the first mirror. The first adjusting element changes at least either the average refractive index of the optical waveguide region or a thickness of the optical waveguide region to change a direction of the light emitted through the first mirror.