PURPOSE: To provide a pleat forming device for curtain wherein even if a pleat part is pulled downward, the part at which a suspension part is engaged with a support rod is not disconnected from the support rod and the shape of the pleat part is prevented from being deformed, by providing the support rod on the side opposite to engaging openings based on grip pieces.

CONSTITUTION: A main body 19 is composed of a gripping member 20, a basic part 11 in the main body 19, engaging openings 12 formed on the basic part 11, engaging projections 13, each of which protrudes from the inside of the engaging opening 12, and a pair of grip pieces 14 formed protruding from the basic part 11, and the respective grip pieces 14 each are formed in the vicinity of the engaging openings 12. A support rod 15 formed protruding from the basic part 11 is provided on the side opposite to the engaging openings 12 based on the grip pieces 14. A pair of gripping parts 16 on the gripping member 20 are linear and a joint part 17 joining the gripping parts 16 is almost semicircular. Curved parts 18 formed at the top end of the gripping member 20 can separately be engaged with the engaging projections 13. In order that pleats are formed on a curtain having a suspension part 10 at the upper part thereof, two pleat parts 10a are formed by bending the suspension part 19 and holding the suspension part 10 between the main body 19 and the gripping member 20.