An over having an improved exhaust structure capable of discharging a fluid of the inside of a cooking chamber at a constant rate, the oven including a cooking chamber cooking food, a machine chamber disposed at an upper side of the cooking chamber and accommodating an electronic component, a cooling fan unit disposed at an inside of the machine chamber to cool the machine chamber, and a flow passage guide communicating with an inside the cooking chamber and an inside of the cooling fan unit such that a fluid of the inside of the cooking chamber is introduced to the inside of the cooling fan unit, wherein the cooling fan unit includes a cooling fan configured to suck a fluid of the inside the machine chamber and blow the fluid to the outside environment.