An opening and closing device of an air vent for a vehicle is provided for raising or lowering the air vent so as to open or close a ventilating part. The opening and closing device includes first and second link parts rotatably provided at both sides of the ventilating part, a hydraulic cylinder part having one side fixed to the air vent and the other side connected to the first link part, a piston rod part having one side connected to the second link part and the other side slidably coupled to the hydraulic cylinder part, and an adjusting part fixing the piston rod part to not slide into the hydraulic cylinder part or release the piston rod part to be slidable.