A steam type clothing flattening device includes an electrical heating tray unit and a soleplate unit. The electrical heating tray unit is heated electrically to vaporize water in an upper vaporization chamber thereof, and has a discharge port for discharge of vapor from the upper vaporization chamber. The soleplate unit is coupled to an underside of and heated by the electrical heating tray unit. The soleplate unit cooperates with the electrical heating tray unit to define a lower vaporization chamber in communication with the discharge port, and has a plurality of vapor outlets extending through a bottom surface thereof for outletting vapor from the lower vaporization chamber.