A cooking appliance comprising: a casing provided with a cooking space therein; a heating unit configured to heat the cooking space: an electronic component space provided outside the casing; a circuit board disposed in the electronic component space; a supporter configured to space the circuit board from the casing and support the circuit board; a cooling fan configured to generate a flow of cool air passing through a cool air passage that is surrounded by the casing, the circuit board and the supporter; a temperature measuring unit installed at the supporter and configured to measure temperatures in the cool air passage; and a controller configured to control an operation of the heating unit, wherein, the electronic component space is disposed upon the casing, and the supporter comprises an air guide disposed laterally adjacent to the circuit board, protruding from the casing upward, and blocking a lateral side of the cool air passage, characterized in that controlling the operation of the heating unit by the controller is performed based on an increase rate of temperatures measured by the temperature measuring unit, and the temperature measuring unit is installed at the air guide. a casing provided with a cooking space therein; a heating unit configured to heat the cooking space: an electronic component space provided outside the casing; a circuit board disposed in the electronic component space; a supporter configured to space the circuit board from the casing and support the circuit board; a cooling fan configured to generate a flow of cool air passing through a cool air passage that is surrounded by the casing, the circuit board and the supporter; a temperature measuring unit installed at the supporter and configured to measure temperatures in the cool air passage; and a controller configured to control an operation of the heating unit, wherein, the electronic component space is disposed upon the casing, and the supporter comprises an air guide disposed laterally adjacent to the circuit board, protruding from the casing upward, and blocking a lateral side of the cool air passage, characterized in that controlling the operation of the heating unit by the controller is performed based on an increase rate of temperatures measured by the temperature measuring unit, and the temperature measuring unit is installed at the air guide. an electronic component space provided outside the casing; a circuit board disposed in the electronic component space; a supporter configured to space the circuit board from the casing and support the circuit board; a cooling fan configured to generate a flow of cool air passing through a cool air passage that is surrounded by the casing, the circuit board and the supporter; a temperature measuring unit installed at the supporter and configured to measure temperatures in the cool air passage; and a controller configured to control an operation of the heating unit, wherein, the electronic component space is disposed upon the casing, and the supporter comprises an air guide disposed laterally adjacent to the circuit board, protruding from the casing upward, and blocking a lateral side of the cool air passage, characterized in that controlling the operation of the heating unit by the controller is performed based on an increase rate of temperatures measured by the temperature measuring unit, and the temperature measuring unit is installed at the air guide.