The invention relates to microorganism producing 5′-xanthylic acid. A 3,4-dehydro-DL-proline resistant Corynebacterium ammoniagenes CJXPK001 strain is provided for producing 5′-xanthylic acid. It is a mutant strain of Corynebacterium ammoniagenes KFCC 10743 having a lower resistance to 3,4-dehydro-DL-proline. The mutant strain is not affected by osmotic pressure caused by accumulated, highly concentrated solute in a culture medium, and it can produce 5′-xanthylic acid at a high yield and concentration rate.