A liquid injector stores data of operating conditions of a liquid injection mechanism for regions to be imaged, and also stores data of schematic images of a plurality of body sections and schematic images of regions to be imaged in association with each other. The liquid injector displays the schematic images in the shape of a human body. When one of the schematic images of the corresponding regions is selected, the liquid injector reads the data of corresponding operating conditions, and controls operation of the liquid injection mechanism according to the read operating conditions. When the operator manually selects one of the schematic images of the body sections and then manually selects one of the schematic images of the corresponding regions, the liquid injector automatically injects a contrast medium into the subject under operating conditions corresponding to the selected region to be imaged.