The present invention provides a rapid prototyping device and a three-dimensional object prototyping method in three-dimensional printing. The prototyping device comprises a first photosensitive drum, a second photosensitive drum, a printing table, a transferring belt, and a light source. A first developer image generated on the first photosensitive drum is transferred by the transferring belt to the printing table, is irradiated by light, and then is solidified into a solid layer; a second developer image generated on the second photosensitive drum is transferred by the transferring belt to an area, excluding the solid layer, on the printing table; and the printing table is located below the transferring belt in a vertical direction. In the vertical direction, the upper surface of the solid layer on the printing table and the upper surface of the second powder-like developer image lie in the same horizontal plane. The prototyping method mainly comprises: generating, by using a first photosensitive drum, a three-dimensional object that can be irradiated by light and then solidified, and generating, by using the second photosensitive drum, a powder accumulation area that can support the three-dimensional object.