Provided is a cooking appliance. The cooking appliance includes a cavity assembly having a cooking chamber and a door that selectively opens or closes the cooking chamber. The cavity assembly includes a cavity including a plurality of plates defining a top surface, a bottom surface, and both side surfaces of the cooking chamber, wherein a first flange part is disposed on each of front end of the plurality of plates, and a front plate having an entrance opening through which food enters into the cooking chamber, the front plate including a second flange part. The first flange part and the second flange part line-contact each other.