An air conditioning device for an electric vehicle includes: a housing having an air conditioning passage connecting an air inlet port to an air discharge port; an evaporator, an air heater, and an electric heater, which are positioned in series in the air conditioning passage in the housing; and a bypass door positioned after the evaporator in the air conditioning passage in the housing and configured to selectively allow some of air passing through the evaporator to bypass the air heater and the electric heater to the air discharge port.