Disclosed herein is a microwave oven having an improved structure with which foods can be effectively heated. The microwave oven includes: a housing including a cooking chamber having a bottom surface; at least one first reflective portion formed on the bottom surface of the cooking chamber; a magnetron provided to generate microwave radiation; and a tray disposed apart from the bottom surface of the cooking chamber and supporting food to be heated. The at least one first reflective portion extends a given height (h) above a reference level (RL).