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 (51, 151, 251, 351, 451, 551) formed on a longitudinal center portion of the outer air duct wall, the protruding portion (51, 151, 251, 351, 451, 551) protruding toward the inner air duct wall, the protruding portion (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) formed on a longitudinal center portion of the outer air duct wall, the protruding portion (51, 151, 251, 351, 451, 551) protruding toward the inner air duct wall, the protruding portion (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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 (51, 151, 251, 351, 451, 551) 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.