The invention provides a steam injection type washing machine, which comprises a tub for accommodating wash water; a drum rotatably installed in the tub 4; a drive unit adapted to rotate the drum; and a steam supply unit with a wash tank, a water supply valve, a heater adapted to heat wash water, a water supply line, a temperature sensor, an inlet for the wash water to enter and an outlet for discharging the steam; a water supply unit for supplying water to the steam supply unit; and a circulating pump for pumping wash water in the tub to the upper part of the tub again.