A vehicle air conditioner includes a casing, a heater core that heats an air flow by heat exchange between the air flow and a heat medium, an electric heater that heats an air flow by an electric power, and a determiner that determines whether a temperature of the heat medium is equal to or lower than a predetermined temperature. When the determiner determines that the temperature of the heat medium is equal to or lower than the predetermined temperature, an air flow introduced into a casing is heated by the electric heater and flows toward the vehicle interior without passing through the heater core.