An air conditioner, comprising: a casing; an air blowing part; and a heat exchanger, the casing comprising a panel having at least one air inlet and at least one air outlet formed therein to be open toward a target space, the heat exchanger being arranged in a flow passage of air that is sucked into the casing through the air inlet and blown out to the target space through the air outlet, wherein an air duct having the air outlet as an outlet is defined by a heat exchanger outlet-side wall, an opposing wall opposed to the heat exchanger outlet-side wall, and two side walls (12, 312) connecting both ends of the heat exchanger outlet-side wall and both ends of the opposing wall to each other, wherein an airflow direction flap is arranged at the air outlet so as to be rotatable, wherein the airflow direction flap comprises a main body, a support plate formed at each longitudinal end portion of the main body, and a rotation shaft positioned on a part of the corresponding support plate side opposite to the main body, wherein each of the side walls comprises a first portion configured to support the airflow direction flap in a rotatable manner, and a second portion (12b, 112b, 212b) positioned on and upstream of the first portion, wherein an air velocity reducing portion (18, 118, 218), which is configured to reduce a velocity of a current of the air passing through a space between each of the side walls and each of the support plates, constructed by the first portion and the second portion (12b, 112b, 212b) is arranged in the air duct having the air outlet as the outlet, and wherein the second portion is closer, than the first portion, to a longitudinal center portion of the air duct having the air outlet as the outlet, characterized in that the second portion is more distant, than an end of the support plate on which the rotation shaft is positioned, from the longitudinal center portion of the air duct having the air outlet as the outlet. a casing; an air blowing part; and a heat exchanger, the casing comprising a panel having at least one air inlet and at least one air outlet formed therein to be open toward a target space, the heat exchanger being arranged in a flow passage of air that is sucked into the casing through the air inlet and blown out to the target space through the air outlet, wherein an air duct having the air outlet as an outlet is defined by a heat exchanger outlet-side wall, an opposing wall opposed to the heat exchanger outlet-side wall, and two side walls (12, 312) connecting both ends of the heat exchanger outlet-side wall and both ends of the opposing wall to each other, wherein an airflow direction flap is arranged at the air outlet so as to be rotatable, wherein the airflow direction flap comprises a main body, a support plate formed at each longitudinal end portion of the main body, and a rotation shaft positioned on a part of the corresponding support plate side opposite to the main body, wherein each of the side walls comprises a first portion configured to support the airflow direction flap in a rotatable manner, and a second portion (12b, 112b, 212b) positioned on and upstream of the first portion, wherein an air velocity reducing portion (18, 118, 218), which is configured to reduce a velocity of a current of the air passing through a space between each of the side walls and each of the support plates, constructed by the first portion and the second portion (12b, 112b, 212b) is arranged in the air duct having the air outlet as the outlet, and wherein the second portion is closer, than the first portion, to a longitudinal center portion of the air duct having the air outlet as the outlet, characterized in that the second portion is more distant, than an end of the support plate on which the rotation shaft is positioned, from the longitudinal center portion of the air duct having the air outlet as the outlet.