A visualizing agent quantity display control system includes a first container, a second container, a detection unit, a display unit, a control unit. The second container, which is replaceable, contains the visualizing agent to be supplied to the first container. The detection unit detects a quantity of the visualizing agent contained in the second container. The control unit causes the detection unit to detect a remaining quantity of the visualizing agent in the second container except the visualizing agent which decreases when an operation of supplying the visualizing agent in the second container to the first container has first been executed. The control unit causes a display unit to display information indicating that the remaining quantity of the visualizing agent in the second container is full regardless of the quantity of the visualizing agent which decreases when the operation has first been executed.