PURPOSE: To provide the operating method of a clothes unwrinkling steam device of laundry smoothly filling steam in a steam box and unwrinkling the laundry efficiently and effectively.

CONSTITUTION: Laundry 8 is suspended in a steam box 6 provided with a ventilation path 1, an outside air guide cold-air damper 2, an outside air guide dry damper 3, a hot-air damper 4, a discharge port 5, a blast device 7, a steam injection device 9, a heating device 10, steam is filled in the steam box 6 by the discharge port 5, blast device, and steam injection device 9, and steam injecting, steaming, drying, and steam discharging operations are performed in sequence by a control system 11.