Vehicular air conditioning apparatus

In a vehicular air conditioning apparatus (10), a driving force transmission mechanism (22) is provided, which causes a switching operation of an air mixing damper (18) disposed in a casing (12) to be performed under a driving action of a drive source (20). The driving force transmission mechanism (22) includes a first gear (44) installed on the drive source (20), a second gear (46) enmeshed with the first gear (44), and a damper shaft (50), which is enmeshed with the second gear (46) and with a rack member (32) of the air mixing damper (18). The second gear (46) is supported rotatably on a gear holder (48), while the gear holder (48) is installed on a side surface of the casing (12).