A microwave oven including: a main casing forming a component compartment and a cooking compartment and formed with a component compartment through portion communicating with the component compartment; a fan assembly coupled to the main casing, and including an exhaling fan blowing air toward the component compartment through portion to cool the component compartment and a fan motor driving the exhaling fan; and a guide unit mounted to the component compartment through portion and guiding the air blown by the exhaling fan toward a heating component accommodated in the component compartment.