Abstract: An illusionary light source device is disclosed. The illusionary light source device includes a light emitting unit and a picture layer. The picture layer can partially block and partially transmit the light from the light emitting unit. Blocking areas and transmitting areas of the picture layer can be properly arranged to form a picture. The picture is therefore presented by the transmitting light. The illusionary light source device further includes a partial-light-blocking layer. The partial-light-blocking layer also can partially block and partially transmit the light from the light emitting unit. The partial-light-blocking layer is disposed between the light emitting unit and the picture layer. Light is emitted through the partial-light-blocking layer and then presented on the picture layer. By the relative motion between any two of the light emitting unit, the partial-light-blocking layer and the picture layer, the picture layer presents a wonderful light show.