The present invention relates to a novel biomarker for predicting sensitivity to a poly ADP ribose polymerase (PARP) inhibitor, and a use thereof, and more specifically, the present invention provides: a biomarker for predicting sensitivity to the PARP inhibitor, the biomarker comprising the p53 gene and/or the DNA-dependent protein kinase (DNA-PK) gene; a composition for predicting sensitivity to the PARP inhibitor, the composition comprising a pharmaceutical preparation for measuring the degree of expression of the gene in the biomarker, or the degree of expression of the protein of the gene; a kit for predicting sensitivity to the PARP inhibitor, the kit comprising the composition; a method for predicting sensitivity to the PARP inhibitor; a sensitivity enhancer for enhancing the sensitivity of a subject to the PARP inhibitor; and a pharmaceutical composition for preventing or treating cancer, the pharmaceutical composition comprising, as active ingredients, the sensitivity enhancer and the PARP inhibitor. According to the present invention, the present invention has an excellent effect of predicting sensitivity to the PARP inhibitor, and thus may be usefully employed for treating colon cancer.