The present invention relates to drum type washing machines, and more particularly, to a new type of steam generator for a drum type washing machine, which enables fast and effective washing and drying of laundry, and can provide a refresh effect of removal of wrinkles form, and sterilization of the laundry. For this, a steam generator (600) includes a steam generating portion (610) having a water supply inlet (612) at one side and an outlet (613) at the other side, and a space (611) between the water supply inlet (612) and the outlet (613), a water supply flow line (620) connected to the water supply inlet (612) for guiding the water to the space, a discharge flow line (630) connected to the outlet (613) for guiding a flow of steam generated at the space, a bypass flow line (660) connected to the water supply flow line (620) for discharging the water overflowing from the steam generating portion (610) in a case water is supplied in a state the outlet (613) and/or the discharge flow line (630) are blocked, and a heater (640) for heating the water supplied through the water supply inlet (612) to generate the steam.