An electric oven, comprising: an outer case including a top plate defining a top surface of the electric oven and lateral plates having an external air inlet; a cavity enclosed by the outer case and defining a cooking chamber therein, the cavity including an inner cavity and an outer cavity enclosing the inner cavity; a door pivotally provided on a front surface of the cavity; a supporting plate disposed between a top surface of the outer cavity and the outer case; at least one electrical component (147, 149) on the supporting plate; a control panel mounted on front end portions of the cavity and the outer case; and a guide member above the supporting plate to divide external air introduced into air flowing along a control panel region and air flowing along an electric component region, wherein the electric oven further comprises: a dividing member extending upward from the rear end of the supporting plate to closely contact an undersurface of the top plate, the dividing member isolating a first passage formed under the supporting plate from a second passage formed above the supporting plate, wherein the supporting plate includes at least one communication opening allowing the second passage to communicate with the first passage, wherein a third passage is formed between a back plate of the outer cavity and a back plate of the inner cavity, wherein an upstream side of the third passage is connected to the downstream side of the first passage, such that the air flowing along the first passage flows downward along the third passage, and wherein the communication opening is defined around a side position thereof opposite to the external air inlet, such that an airflow direction in the second passage intersects an airflow direction in the first passage. an outer case including a top plate defining a top surface of the electric oven and lateral plates having an external air inlet; a cavity enclosed by the outer case and defining a cooking chamber therein, the cavity including an inner cavity and an outer cavity enclosing the inner cavity; a door pivotally provided on a front surface of the cavity; a supporting plate disposed between a top surface of the outer cavity and the outer case; at least one electrical component (147, 149) on the supporting plate; a control panel mounted on front end portions of the cavity and the outer case; and a guide member above the supporting plate to divide external air introduced into air flowing along a control panel region and air flowing along an electric component region, wherein the electric oven further comprises: a dividing member extending upward from the rear end of the supporting plate to closely contact an undersurface of the top plate, the dividing member isolating a first passage formed under the supporting plate from a second passage formed above the supporting plate, wherein the supporting plate includes at least one communication opening allowing the second passage to communicate with the first passage, wherein a third passage is formed between a back plate of the outer cavity and a back plate of the inner cavity, wherein an upstream side of the third passage is connected to the downstream side of the first passage, such that the air flowing along the first passage flows downward along the third passage, and wherein the communication opening is defined around a side position thereof opposite to the external air inlet, such that an airflow direction in the second passage intersects an airflow direction in the first passage. a dividing member extending upward from the rear end of the supporting plate to closely contact an undersurface of the top plate, the dividing member isolating a first passage formed under the supporting plate from a second passage formed above the supporting plate, wherein the supporting plate includes at least one communication opening allowing the second passage to communicate with the first passage, wherein a third passage is formed between a back plate of the outer cavity and a back plate of the inner cavity, wherein an upstream side of the third passage is connected to the downstream side of the first passage, such that the air flowing along the first passage flows downward along the third passage, and wherein the communication opening is defined around a side position thereof opposite to the external air inlet, such that an airflow direction in the second passage intersects an airflow direction in the first passage.