Provided is a damper opening/closing mechanism of a vehicle air-conditioning device, the damper opening/closing mechanism being configured such that a pin (28) of a damper lever (26) is fitted in a cam groove (24) of a link plate (22) rotatably driven by a stepping motor and that a damper (19) is opened/closed through the damper lever (26) rotated by rotation of the link plate (22). One end portion of the cam groove (24) for reference positioning of the stepping motor is in such a shape that a connection surface (32) not contacting an outer peripheral surface of the pin (28) connects between the point of contact of the outer periphery of the pin (28) with one end surface of the cam groove (24) and the point with a side wall surface (24A) of the cam groove (24) when the damper (19) is in a closed state.