To form a three-dimensional object with low-cost materials and devices by injecting high pressure fluid flow to a material to be processed, and changing a relative position to each other.

This device is constituted of a fixed platform 2 which supports a work 1 to be processed, an injecting device 3 which injects high pressure fluid flow to the work 1 to be processed, and a moving mechanism 4 which changes a relative position between the work 1 processed and the injecting device 3. The fixed platform 2 prevents the work 1 to be processed from moving when water is injected and cuts the work 1 to be processed by injecting high pressure water to the part 1 to be processed which is fixed at the fixed platform. A nozzle 31 is moved on a flat surface which is positioned on the top of the work 1 to be processed by a moving mechanism 4. The relative position between the nozzle 31 and the work 1 to be processed which is fixed at the fixed platform 2 is changed, and the position where high pressure water stream on the surface of the work 1 to be processed is injected is changed. It is thus possible to form a three-dimensional object at low cost in a short time and improve workability in forming the three-dimensional object.