Method for controlling a drying process of a washing and drying machine including a preheating step for tightly closing and heating an inner tub for preparing an environment favorable for vaporization of water by elevating a temperature of the inner tub within a short time period, and a drying step for supplying heated air to the inner tub, to make heat exchange between the heated air and laundry, for drying the laundry, whereby improving a drying performance and reducing occurrence of environmental problem.