An oven, comprising: a casing to form an external appearance of the oven; a cooking compartment positioned at an inside of the casing, and including a first cooking compartment positioned at an upper side and a second cooking compartment positioned at a lower side; a door to open/close the cooking compartment; a divider positioned in between the first cooking compartment and the second cooking compartment; a first circulating fan and a second circulating fan coupled to rear surfaces of the first cooking compartment and the second cooking compartment, respectively; and an inlet unit (41, 42, 44; 410, 420) to introduce outside air to at least one of the first cooking compartment and the second cooking compartment, the oven further comprising: an outlet pipe (51, 52; 150; 440) to communicate the cooking compartment with an outside so as to discharge a predetermined amount of air inside the cooking compartment corresponding to an amount of air introduced from the outside; and a cooling fan configured to discharge the air inside the cooking compartment to the outside through the outlet pipe (51, 52; 150; 440), characterized in that the outlet pipe (51, 52; 150; 440) is coupled to a front outlet hole adjacently provided at an upper portion of the door, wherein at least one of a door flow path (12a, 12b, 12c) is formed at an inside of the door, and wherein the cooling fan is installed at an outer side of the plurality of cooking compartments (11a, 11b) as to lead to a cooling of the door by taking in outside air through the at least one door flow path (12a, 12b, 12c). a casing to form an external appearance of the oven; a cooking compartment positioned at an inside of the casing, and including a first cooking compartment positioned at an upper side and a second cooking compartment positioned at a lower side; a door to open/close the cooking compartment; a divider positioned in between the first cooking compartment and the second cooking compartment; a first circulating fan and a second circulating fan coupled to rear surfaces of the first cooking compartment and the second cooking compartment, respectively; and an inlet unit (41, 42, 44; 410, 420) to introduce outside air to at least one of the first cooking compartment and the second cooking compartment, the oven further comprising: an outlet pipe (51, 52; 150; 440) to communicate the cooking compartment with an outside so as to discharge a predetermined amount of air inside the cooking compartment corresponding to an amount of air introduced from the outside; and a cooling fan configured to discharge the air inside the cooking compartment to the outside through the outlet pipe (51, 52; 150; 440), characterized in that the outlet pipe (51, 52; 150; 440) is coupled to a front outlet hole adjacently provided at an upper portion of the door, wherein at least one of a door flow path (12a, 12b, 12c) is formed at an inside of the door, and wherein the cooling fan is installed at an outer side of the plurality of cooking compartments (11a, 11b) as to lead to a cooling of the door by taking in outside air through the at least one door flow path (12a, 12b, 12c). an outlet pipe (51, 52; 150; 440) to communicate the cooking compartment with an outside so as to discharge a predetermined amount of air inside the cooking compartment corresponding to an amount of air introduced from the outside; and a cooling fan configured to discharge the air inside the cooking compartment to the outside through the outlet pipe (51, 52; 150; 440), characterized in that the outlet pipe (51, 52; 150; 440) is coupled to a front outlet hole adjacently provided at an upper portion of the door, wherein at least one of a door flow path (12a, 12b, 12c) is formed at an inside of the door, and wherein the cooling fan is installed at an outer side of the plurality of cooking compartments (11a, 11b) as to lead to a cooling of the door by taking in outside air through the at least one door flow path (12a, 12b, 12c).