To crease trousers at the time of hanging the trousers on a hanger.

This crease working device 1 of the trousers is provided with a trouser hanging bar 2 for folding the approximate center part of the trousers 10 and hanging them, a trouser hanger main body 3 for holding the trouser hanging bar 2 and one set of crease formation parts 4a and 4b at least one of which is freely turnable to the trouser hanger main body 3 for forming the creases of the trousers 10 hung to the trouser hanging bar 2 by being attached to the trouser hanger main body 3. The crease formation parts 4a and 4b are provided with opening/closing operation parts 43 for clamping the trousers 10. The crease positions of the trousers are clamped by the crease formation parts 4a and 4b, parts near the crease parts of the trousers 10 are pressurized by the pressing force of a pressing member provided in the crease formation parts 4a and 4b and the clear creases are formed on the trousers.