A method of adjusting a resonance frequency in an optical scanning device containing: providing the optical scanning device having a substrate composed of a substrate main body and two cantilever beam portions, a drive source, a mirror portion, and a supporting component for fixing the substrate main body at a fixed end; and reducing an area of the substrate which protrudes from the fixed end to an outside of the supporting component, thereby to increase the resonance frequency; or alternatively, increasing the area of the substrate which protrudes from the fixed end to the outside of the supporting component, thereby to reduce the resonance frequency.