In an optical scanning device, a lower frame includes a first wall contacting an optical element, a second wall connected to a second-wall connecting portion of the first wall, a third wall connected to a third-wall connecting portion of the first wall, and a biasing member having a first end contacting the optical element and a second end supported by a scanner frame to press the optical element against the first wall. The second wall extends in a traverse direction angled with respect to a direction in which the first wall extends. The third wall extends in a direction facing away from an optical element side of the first wall on which the optical element is located. The optical element is in contact with at least one position of the first wall which position is between the second-wall connecting position and the third-wall connecting position.