An optical scanning device including: a first mirror having a first reflecting surface; a second mirror having a second reflecting surface; two non-waveguide regions disposed between the first and second mirrors and that are spaced apart from each other in a first direction parallel to at least either the first reflecting surface or the second reflecting surface; and an optical waveguide region disposed between the first and second mirrors and that is sandwiched between the two non-waveguide regions. The optical waveguide region propagates light in a second direction that crosses the first direction. 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 the refractive index of the common material exists.