Since the K-ras oligonucleotide microarray of the present invention can detect K-ras mutations by applying a competitive DNA hybridization method to the oligonucleotides spotted on a solid matrix different from the previously reported method for detecting a mutation, it makes the more precise analysis and can reduce experimental cost and time. Accordingly, the K-ras oligonucleotide microarray of the present invention can be used in studies to detect K-ras mutations and unravel the signal transduction mechanism and tumorigenesis related to K-ras gene. Further, since the microarray of the present invention can be applied to other genes having mutational hot spot regions such as K-ras, it has wide applicable range.