A liquid injector for injecting at least a contrast medium into a subject whose fluoroscopic image is to be captured by an imaging diagnostic apparatus, wherein said contrast medium is available in a plurality of types having different concentrations of an effective component, said liquid injector comprising: a liquid injection mechanism for injecting at least said contrast medium into said subject; an injection control means for controlling operation of said liquid injection mechanism under the operating conditions whose data have been read; and a display and touch panel; said display and touch panel being adapted to display a plurality of body sections in schematic images of shapes of a human body and accepting selection of one of said body sections when one of the displayed plurality of body sections is touched; wherein when one of the body sections is selected, said display and touch panel is further adapted to display at least one of a plurality of regions to be imaged of the human body in schematic images of shapes of regions and accept selection of one of said regions to be imaged when one of the displayed regions to be imaged is touched; and said injection control means is adapted to perform: reading out, from condition storage means, a base-operation condition including a predetermined injection time for the injection and a necessary dose of effective component of the contrast medium per unit weight of the subject, each of which is for the selected region, and a concentration of the effective component, calculating necessary volume of the contrast medium based on the read out necessary dose of effective component per unit weight and concentration of the effective component, calculating a time-injection rate pattern as operation condition based on the calculated necessary volume of the contrast medium and the base-operation condition, and performing the injection of said contrast medium based on the calculated time-injection rate pattern by controlling the operation of said liquid injection mechanism. a liquid injection mechanism for injecting at least said contrast medium into said subject; an injection control means for controlling operation of said liquid injection mechanism under the operating conditions whose data have been read; and a display and touch panel; said display and touch panel being adapted to display a plurality of body sections in schematic images of shapes of a human body and accepting selection of one of said body sections when one of the displayed plurality of body sections is touched; wherein when one of the body sections is selected, said display and touch panel is further adapted to display at least one of a plurality of regions to be imaged of the human body in schematic images of shapes of regions and accept selection of one of said regions to be imaged when one of the displayed regions to be imaged is touched; and said injection control means is adapted to perform: reading out, from condition storage means, a base-operation condition including a predetermined injection time for the injection and a necessary dose of effective component of the contrast medium per unit weight of the subject, each of which is for the selected region, and a concentration of the effective component, calculating necessary volume of the contrast medium based on the read out necessary dose of effective component per unit weight and concentration of the effective component, calculating a time-injection rate pattern as operation condition based on the calculated necessary volume of the contrast medium and the base-operation condition, and performing the injection of said contrast medium based on the calculated time-injection rate pattern by controlling the operation of said liquid injection mechanism. reading out, from condition storage means, a base-operation condition including a predetermined injection time for the injection and a necessary dose of effective component of the contrast medium per unit weight of the subject, each of which is for the selected region, and a concentration of the effective component, calculating necessary volume of the contrast medium based on the read out necessary dose of effective component per unit weight and concentration of the effective component, calculating a time-injection rate pattern as operation condition based on the calculated necessary volume of the contrast medium and the base-operation condition, and performing the injection of said contrast medium based on the calculated time-injection rate pattern by controlling the operation of said liquid injection mechanism.