An air conditioner , comprising: at least one air inlet and at least one air outlet formed in a lower portion of the air conditioner ; a wall portion defining one blowing air duct having the one air outlet as an outlet; an airflow direction flap arranged in the one air outlet ; an air sending unit configured to generate a flow of air that is sucked through the air inlet and blown out through the air outlet ; and a heat exchanger arranged in a flow passage of the air that is sucked through the air inlet and blown out through the air outlet , the wall portion comprising an inner air duct wall and an outer air duct wall , a protruding portion formed on a longitudinal center portion of the outer air duct wall , the protruding portion protruding toward the inner air duct wall , the protruding portion being positioned on upstream of the airflow direction flap , wherein, in plan view, the outer air duct wall is at a position more distant from the heat exchanger than the inner air duct wall , wherein, on a plane on the upstream of the airflow direction flap , a distance "D1" between the protruding portion on the center portion of the outer air duct wall in the longitudinal direction of the blowing air duct and a center portion of the inner air duct wall in the longitudinal direction of the blowing air duct is smaller than a distance "D2" between each side portion of the protuding portion of the outer duct wall and rhe inner duct wall , and wherein, in plan view, the protruding portion has a longitudinal length "L2" equal to or larger than one third of a longitudinal length "L1" of the outer air duct wall , wherein, the protruding portion has a protruding height in a transverse direction orthogonal to the longitudinal direction of the blowing air duct , wherein the protruding height increases toward downstream of the blowing air duct . at least one air inlet and at least one air outlet formed in a lower portion of the air conditioner ; a wall portion defining one blowing air duct having the one air outlet as an outlet; an airflow direction flap arranged in the one air outlet ; an air sending unit configured to generate a flow of air that is sucked through the air inlet and blown out through the air outlet ; and a heat exchanger arranged in a flow passage of the air that is sucked through the air inlet and blown out through the air outlet , the wall portion comprising an inner air duct wall and an outer air duct wall , a protruding portion formed on a longitudinal center portion of the outer air duct wall , the protruding portion protruding toward the inner air duct wall , the protruding portion being positioned on upstream of the airflow direction flap , wherein, in plan view, the outer air duct wall is at a position more distant from the heat exchanger than the inner air duct wall , wherein, on a plane on the upstream of the airflow direction flap , a distance "D1" between the protruding portion on the center portion of the outer air duct wall in the longitudinal direction of the blowing air duct and a center portion of the inner air duct wall in the longitudinal direction of the blowing air duct is smaller than a distance "D2" between each side portion of the protuding portion of the outer duct wall and rhe inner duct wall , and wherein, in plan view, the protruding portion has a longitudinal length "L2" equal to or larger than one third of a longitudinal length "L1" of the outer air duct wall , wherein, the protruding portion has a protruding height in a transverse direction orthogonal to the longitudinal direction of the blowing air duct , wherein the protruding height increases toward downstream of the blowing air duct . <EOS>