Disclosed are a ventilation apparatus and an air conditioner including the same. The air conditioner includes a main body including a heat exchanger and a blower fan blowing indoor air to pass through the heat exchanger, and a ventilation apparatus mounted on the main body to ventilate a room, the ventilation apparatus includes a case configured to accommodate a ventilation fan, a ventilation pipe including an inlet tube mounted on an outdoor air inlet of a building and an extension tube connecting a flow path of the case and the inlet tube and detachably connected to the inlet tube, and a ventilation filter installed in the ventilation pipe through a connection portion between the inlet tube and the extension tube to filter out foreign substances in air.