A vehicular air conditioner capable of reducing high-frequency sounds generated when an air mix damper is slightly opened and finely adjusting the temperature around the maximum heating position for improving the temperature controllability is provided. The vehicular air conditioner including an air mix damper that adjusts a flow rate of air delivered into a heating passage including a heater core after being passed through an evaporator and a flow rate of air delivered into a bypass passage that bypasses the heater core. In the vehicular air conditioner, a plurality of asperity portions are formed on a distal-end-side surface of the damper in the width direction of the damper, at which the damper is in contact with a seal surface on a unit case at the maximum heating position, and an elastic insulator having a predetermined thickness is attached to the asperity portions to form asperities similar thereto.