A projection device includes a light beam generator including an incoherent light source assembly, a reflecting mirror arranged on one side of the light beam generator, an interference structure arranged on a reflecting light path of the reflecting mirror and generating a pattern effect, a first gear structure arranged on an outer side of the interference structure, a convex lens arranged on an exit light path of the interference structure; and a motor. A light beam generated by the light beam generator irradiates on one surface of the reflecting mirror along an incident light path of the reflecting mirror and reflects to a side surface of the interference structure. The light beam passes through the interference structure and the convex lens in sequence to form a patterned projection. A second gear structure engaged with the first gear structure is arranged on an output shaft of the motor.