Provided is a jet machining device by which damage to an object to be processed is mitigated. The jet machining device is provided with a rotating-type support material 5 that, when a machining medium 3 is jetted onto the surface of an object to be processed 1, supports the object to be processed 1 from the side thereof that is opposite to a nozzle 4 while the rotating-type support material rotates in a direction in which the object to be processed 1 is conveyed. The rotating-type support material 5 is formed by combining a first rotating-type support material 6 and a second rotating-type support material 7. The first rotating-type support material 6 is provided with first rotating bodies (rollers 6a), and the second rotating-type support material 7 is provided with second rotating bodies (belts 7a). The jet machining device is further provided with discharge openings 8 through which the machining medium 3 can be discharged to a prescribed region.