A cooking appliance has a configuration that allows the heating item mounting unit of a heating chamber to be pulled out, and that can prevent generation of discharge failure by microwaves, without having to form a slide mechanism with a component or material that has high heat-resistance and fire-resistance. The cooking appliance includes a main unit with a heating chamber, a drawer unit arranged movable in the main unit so as to be pulled out from the heating chamber of the main unit, and a slide rail for moving the drawer unit in the main unit. The slide rail is provided outside the heating chamber.