An air conditioner controlling device for a vehicle may include a knob rotatably installed on the front of a case, a cylindrical cam rotatably installed inside the case, interlocked with a shaft of the knob, and having a slot formed in an outer surface thereof, and a lever having one end rotatably mounted to the case and the other end insertedly coupled to the slot of the cylindrical cam to thereby reciprocate the cylindrical cam at the time of rotation of the cylindrical cam, wherein the lever may be insertedly mounted in a portion of the slot formed along the outer surface of the cylindrical cam, and a mounting position and angle of the lever may be thus adjusted, such that a reciprocation direction of the lever may be freely adjusted.