An air conditioner for a vehicle comprising: a first path having a first flow path and a first supply path through which an air taken in through a first air intake flows therein; a second path having a second flow path and a second supply path through which an outside air taken in through an outside air intake flows therein, the outside air is an air outside of a vehicle when the air conditioner is mounted on the vehicle, the second supply path has an air outlet for exhausting air to the outside of the vehicle; and a desiccant material disposed across the first path and the second path, the first flow path and the second flow path being located upstream the desiccant material in the direction of the air flow, the outside air flows through the second path as a regeneration fluid for the desiccant material, wherein the desiccant material in the first path is disposed in a region where an air constantly flows during the air conditioner is in operation, a first blower for supplying the air taken in through the first air intake toward a supply port of a vehicle cabin is provided in the first path, and a first valve for determining the air flows into the first path from among an inside air and the outside air is disposed upstream of the first blower, the inside air is an air in the vehicle cabin when the air conditioner is mounted on the vehicle, characterized in that the air conditioner comprises a first communication port communicating the first flow path with the second flow path, the air flowing into the first path is determined from among the inside air and the outside air by the open and close of the communication port in the first valve. a first path having a first flow path and a first supply path through which an air taken in through a first air intake flows therein; a second path having a second flow path and a second supply path through which an outside air taken in through an outside air intake flows therein, the outside air is an air outside of a vehicle when the air conditioner is mounted on the vehicle, the second supply path has an air outlet for exhausting air to the outside of the vehicle; and a desiccant material disposed across the first path and the second path, the first flow path and the second flow path being located upstream the desiccant material in the direction of the air flow, the outside air flows through the second path as a regeneration fluid for the desiccant material, wherein the desiccant material in the first path is disposed in a region where an air constantly flows during the air conditioner is in operation, a first blower for supplying the air taken in through the first air intake toward a supply port of a vehicle cabin is provided in the first path, and a first valve for determining the air flows into the first path from among an inside air and the outside air is disposed upstream of the first blower, the inside air is an air in the vehicle cabin when the air conditioner is mounted on the vehicle, characterized in that the air conditioner comprises a first communication port communicating the first flow path with the second flow path, the air flowing into the first path is determined from among the inside air and the outside air by the open and close of the communication port in the first valve.