A steam iron comprising a base incorporating a heater, a heat-insulating cover which covers the top surface of the base, a handle unit connected to the heat-insulating cover at its rear portion, and a water tank mounted on the top front portion of the heat-insulating cover capable of being removed forward. The handle unit and the heat-insulating cover forming a water-tank housing space, of which the front and the both lateral sides are opened. The rear portion of the housing space where the handle unit is connected to the heat-insulating cover is narrowed as compared with the front-opening of the housing space. The housing space is so formed as to guide the water tank. By pushing the water tank along the housing space in a straight line, the water tank can be smoothly mounted.