According to an embodiment, a projection device includes: a light source; an optical scanning unit that includes a base unit, a driver fixed to the base unit, and a reflective unit supported by the driver and that drives the reflective unit to scan light from the light source; and a scanned unit configured to be scanned with the light from the optical scanning unit so that a projection image is formed on the scanned unit. The projection device further includes an attachment unit for attaching the projection device to a setting unit of a setting object on which the projection device is set. The attachment unit attaches the projection device to the setting unit such that a direction in which vibration caused by the setting object is equal to or smaller than a predetermined value and a reflective surface of the reflective unit are approximately perpendicular to each other.