Bursaphelenchus xylophilus is the causal agent of pine wilt disease, which is a major forest disease in Japan, Korea, China, Taiwan, and Portugal. A diagnostic method which is rapid, precise, and simple could greatly help the proper management of this disease. Here, we present a novel detection method using loop-mediated isothermal amplification (LAMP) targeting the internal transcribed spacer region of ribosomal DNA of the nematode. Specificity of the primers and LAMP was confirmed using DNA from various nematode species related to B. xylophilus. Our experimental results suggest that LAMP can detect B. xylophilus faster and with higher sensitivity than the traditional diagnostic method. Moreover, because it does not require expensive equipment or specialized techniques, this LAMP-based diagnostic method has the potential to be used under field conditions.