The optical scanning device includes a swingable reflector; a blocking unit that is provided in the reflector to move in linkage with the reflector; and a sensor unit that includes at least a first sensor unit and a second sensor unit, wherein each of the first and second sensor units includes an output unit, which is a light generator or an electromagnetic wave generator configured to output a detection target and a detection unit, which is a light receiver or an electromagnetic wave receiver configured to detect the detection target. The output unit is at a position that faces the detection unit. When the reflector is in a predetermined swing angle range, the blocking plate blocks a path of the detection target between the output unit and the detection unit.