Buckwheat often causes severe allergic reactions in sensitive people. One of the major allergenic proteins in common buckwheat (Fagopyrum esculentum) has been found to be a BW10KD protein. In this study, we developed a PCR method to detect buckwheat ingredients in food using primers corresponding to the allergenic BW10KD gene. Five pairs of oligonucleotide primers successfully enabled PCR amplification of the specific regions of the genomic BW10KD DNA from buckwheat, but no amplification from seven other cereals and beans (barley, wheat, German millet, African millet, soybean, red bean, and black bean). The proposed PCR method was applied to analyze 12 processed foods (buckwheat flour, buckwheat noodle, buckwheat jelly, wheat noodle, instant noodle, black sesame gruels, sunsik, cookie, misutkaru, and three kinds of cereal); among them, only three samples including buckwheat flour, buckwheat noodle and buckwheat jelly showed a positive reaction to the detection. This PCR method was able to detect as little as 1 ng of common buckwheat DNA. This rapid and specific PCR method would be applicable to detect allergenic buckwheat ingredients in food.