A washing and drying machine includes: a washing drum for accommodating the washings and rotating under a driving force of a motor; an air supply portion for supplying air into the washing drum; a heating portion configured to heat the air to be supplied into the washing drum when turned on and stop heating when turned off; and a control portion for controlling the motor, the air supply portion and the heating portion to execute a washing and drying operation. A drying procedure in the washing and drying operation includes main drying treatment repeated for multiple times. During each time of the main drying treatment, the control portion is configured to keep the heating portion being on within a first period, and keep the heating portion being off within a second period different from the first period, and the second period is longer than the first period.