To provide a contrast medium injector where a sanitary aspect is excellent, maintenance is simplified and costs are reduced.

The contrast medium injector 1 is provided with: a contrast medium injection tube 11 for connecting a contrast medium container 31 with a rectum catheter 100; an air injection tube 12 for connecting an air pump 21 with the rectum catheter 100; a discharge tube 13 for connecting a discharge container 32 for housing a discharged content with the rectum catheter 100; a communication tube 14 for communicating the discharge container 32 with the contrast medium injection tube 11; a check valve 82 which makes it possible to circulate the communication tube 14 from the side of the discharge container 32 only to the contrast medium injection tube 11; and a contrast medium pump 22 which sends the contrast medium 310 to the side of the rectum catheter 100 through the contrast medium injection tube 11 by normal rotation, and generates negative pressure in the discharge container 32 through the communicating tube 14 by reverse rotation to suck and house the content in the discharge container 32 through the discharge tube 13.