A ventilation apparatus includes a housing having an outdoor air inlet, an outdoor air outlet, an indoor air inlet, and an indoor air outlet; a partition dividing an inner space of the housing into a ventilation space and an air conditioning space; a total heat exchange element inside the ventilation space and having four side edges respectively disposed to face four side surfaces of the housing; four partition walls configured to respectively connect the four side edges of the total heat exchange element and the four side surfaces of the housing to partition the ventilation space into an outdoor air discharge space, an indoor air inlet space, and an indoor air discharge space; guide ducts respectively provided in the outdoor air discharge space, the indoor air inlet space, and the indoor air discharge space; and a bypass duct branching from the guide duct provided in the indoor air inlet space.