An oven having an improved hinge structure of a door, which is capable of preventing deformation of the door and opening a part of a plurality of cooking chambers is provided. The oven includes a main body, a cooking chamber provided inside of the main body, a first door rotatably coupled to the main body by a first hinge unit to open or close the cooking chamber, the first door including a door frame having an opening, at least one reinforcing unit coupled to the door frame, and configured to prevent deformation of the first door, a second door rotatably coupled to the first door, and configured to open or close the opening, and a second hinge unit configured to enable the second door to be rotatably coupled to the first door, and including a hinge shaft positioned behind a front surface of the first door.