A steam generator includes: a water storage chamber which stores water therein; a heating portion which heats water in the water storage chamber to generate steam; a water supply device which supplies the water storage chamber with water; a water discharge passage which discharges water through a water discharge port defined in the water storage chamber; a steam spout port which spouts the steam generated in the water storage chamber therethrough; and a rib integrally formed with an inner wall surface of the water storage chamber so as to cross an inside of the water storage chamber, the rib having a plurality of openings defined therein, wherein the openings are smaller than the water discharge port.