AIR CONDITIONER FOR VEHICLE

An air conditioner for a vehicle includes: a case that forms an air passage; and a filter arranged inside the case. The case has an opening for attaching/detaching the filter. The case has a guide unit provided on an inner wall surface of the case to guide a movement of the filter. The guide unit has a positioning portion to determine a position of the filter in a filter mounted state, and a service portion located between the positioning portion and the opening. The case has a water prevention rib protruding from the inner wall surface so as to extend in a direction intersecting a flow of air at a position upstream of the service portion.