A light scanning device includes: a light source which emits light; a frame which supports the light source; an oscillating mirror which rotationally oscillates about a first axis to reflect the light emitted from the light source; a mirror holder which holds the oscillating mirror; a beam member which extends in a first direction orthogonal to the first axis and which is longer than the mirror holder in the first direction; a first fixing member which fixes the mirror holder to the beam member; and a second fixing member which fixes the beam member to the frame.