An optical assembly includes an optical element including a reflection surface to reflect light in a first axis direction, a holder to hold the optical element, a case to support the holder, a first swing mechanism to swing the holder around a first swing axis, and a second swing mechanism to swing the holder around a second swing axis perpendicular to the first swing axis. The holder includes first and second protrusions. The case includes first and second recesses. Each of the recesses includes a first side surface located on one side in the axial direction of the second swing axis and a second side surface located on the other side with respect to the corresponding protrusion. At least one of the first and second side surfaces includes an inclined surface inclined with respect to the second swing axis.