An under cover for a heat suction is provided and includes a stagnant-air inlet unit into which stagnant air formed in an engine room is drawn and a communication pipe that is configured to communicate with the stagnant-air inlet unit and transmit the stagnant air, drawn into the stagnant-air inlet unit, to an under cover body. A stagnant-air outlet unit is configured to communicate with the communication pipe to exhaust the stagnant air, transmitted to the under cover body, out of the under cover body through the stagnant-air outlet unit, and the stagnant-air outlet unit is mounted to the under cover body.