Air conditioning system for vehicles

An air conditioning system for vehicles having an air conditioning unit (1) which has an air path (2) extending in a horizontal direction, an evaporator (3), a heater core (4) and an air mixing door (5) characterized in that the evaporator (3) is disposed so as to be inclined relative to an extending direction of the air path (2) at an angle in a range of 15 to 30 degrees, and the heater core (4) is disposed to be inclined in the same direction as that of the evaporator (3). While a desirable air conditioning performance can be maintained, the air conditioning system can be made small, particularly, thin, and an air conditioning system suitable for work vehicles can be provided.