Disclosed herein is a microwave oven, which is provided with a toasting cavity in addition to a microwave cooking cavity, thus making well-toasted breads. The microwave oven includes a cabinet which is partitioned into a microwave cooking cavity, a toasting cavity, and a machine room. A microwave generating unit is installed in the machine room to irradiate microwaves into the microwave cooking cavity. A heating unit is installed in the toasting cavity to heat the toasting cavity. A ventilating unit functions to ventilate the toasting cavity.