An air conditioning device for a vehicle includes: a housing having an inside divided into an inflow space, a heat exchange space, and an outflow space, which are straightly arranged, and having a plurality of discharge ports, which communicates with an interior, at the inflow space; a blowing unit disposed at the inflow space of the housing and configured to blow air; a heat exchange unit disposed at the heat exchange space of the housing and configured to adjust a temperature of conditioned air by exchanging heat with air; and an opening-closing door disposed at the outflow space of the housing and configured to open and close the plurality of discharge ports such that conditioned air at an adjusted temperature selectively flows to the plurality of discharge ports. The air conditioning device adjusts the temperature of conditioned air for respective modes and reduces a flow resistance of air.