PURPOSE: To allow a sewing machine to simultaneously embroider the same pattern on a curved material and a flat one without changing embroidery data in particular by rotating a curved cloth extension frame in synchronization with the travel of a movable frame in the direction of Y by controlling the rate of rotation of the curved cloth extension frame and the rate of movement of the movable frame in order that the correspondence of them is one-to-one.

CONSTITUTION: One ends 20a, 22a of wires 20, 22 are held to a curved cloth extension frame 15 for a curved material, and the other ends 20b, 22b to a movable frame 11. The one end 20b of the wire 20 and that 22b of the wire 22 are extended in parallel in the direction of Y to equalize the radius of curvature of turns of wires 20, 22 and that of the frame 15. Thus, when the movable frame 11 travels in the direction of Y, the wires 20, 22 are extended in that direction interlocking with the travel, and the rate of rotation of the frame 15 and the rate of travel of a flat cloth extension frame 12 are equal. In this way, embroidering of the same pattern simultaneously on a curved material and a flat one is possible.