An optical scanning device comprising: a first mirror; a second mirror facing the first mirror; an optical waveguide layer that is disposed between the first mirror and the second mirror and that propagates inputted light as propagating light; a pair of electrodes sandwiching the optical waveguide layer; and a driving circuit (110, 210) that applies a voltage to the pair of electrodes, wherein the first mirror, the second mirror, and the optical waveguide layer have respective structures extending in a same direction, wherein the first mirror allows part of the propagating light propagating through the optical waveguide layer to pass through and be emitted to outside of the optical waveguide layer as emission light, characterized in that the optical waveguide layer contains a liquid crystal material or an electrooptical material, wherein, when the voltage is not applied to the pair of electrodes, (i) an angle between an alignment direction of the liquid crystal material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, or (ii) an angle between a direction of a polarization axis of the electrooptical material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, and wherein the driving circuit (110, 210) applies the voltage to the pair of electrodes to change a refractive index of the liquid crystal material or the electrooptical material for the propagating light propagating through the optical waveguide layer to thereby change a direction of the emission light emitted from the optical waveguide layer. a first mirror; a second mirror facing the first mirror; an optical waveguide layer that is disposed between the first mirror and the second mirror and that propagates inputted light as propagating light; a pair of electrodes sandwiching the optical waveguide layer; and a driving circuit (110, 210) that applies a voltage to the pair of electrodes, wherein the first mirror, the second mirror, and the optical waveguide layer have respective structures extending in a same direction, wherein the first mirror allows part of the propagating light propagating through the optical waveguide layer to pass through and be emitted to outside of the optical waveguide layer as emission light, characterized in that the optical waveguide layer contains a liquid crystal material or an electrooptical material, wherein, when the voltage is not applied to the pair of electrodes, (i) an angle between an alignment direction of the liquid crystal material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, or (ii) an angle between a direction of a polarization axis of the electrooptical material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, and (i) an angle between an alignment direction of the liquid crystal material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, or (ii) an angle between a direction of a polarization axis of the electrooptical material and the direction in which the optical waveguide layer extends is 15 degrees or less, or 75 degrees or more and 105 degrees or less, and wherein the driving circuit (110, 210) applies the voltage to the pair of electrodes to change a refractive index of the liquid crystal material or the electrooptical material for the