Provided is a built-in cooking appliance. According to the built-in cooking appliance, the inside of the cooking appliance is effectively cooled and the inside can be waterproofed without protruding the top plate above the cabinet. Therefore, cooling efficiency, stability in using, convenience in cleaning, esthetic feeling, and reliability of a product can be improved. The built-in cooking appliance includes a top plate, a main body below the top plate, a fan, a cabinet, a gap portion, and a top frame. At least a heating unit is disposed inside the main body. The fan forms a cooling passage inside the main body. The plate is installed on the cabinet. The gap portion defines at least a portion of the cooling passage, and is formed by at least an edge on one side of the top plate and the cabinet separated from each other. The top frame covers the gap portion.