Ventilating system including a total heat exchanger at a region where an air supply duct, a passage for supplying outdoor air to a room, and an air discharge duct, a passage for discharging room air to an outside of the room, cross for making room air and outdoor air to heat exchange, an air supply fan connected to the air supply duct for drawing the outdoor air and discharging the outdoor air to the room, an air discharge fan connected to the air discharge duct for drawing the room air and discharging the room air to an outside of the room, and a flow guide between the air supply/discharge fans and the total heat exchanger for guiding flow directions of the room air and the outdoor air, thereby reducing a flow resistance and making the heat exchange efficient.