Bursaphelenchus xylophilus (Bx) is the main plant-parasitic nematode of the Japanese Black Pine (Pinus thunbergii), Red Pine (Pinus densiflora) and Korean Pine (Pinus koraiensis) in the South Korea. Until now, the nematode morphological classification or PCR method using specific marker of Bx were used for the diagnosis of pine wilt disease. However, both methods have a disadvantage that these take a long time to confirm the result. Thus, these methods can not be used quickly at the newly damaged regions. For above the reasons, we had been developed the diagnostic method for Bx combining direct gDNA extraction buffer (DAP) with Recombinase Polymerase Amplification (RPA). This method is able to directly use mixed lysates extracted from Bx-infected pinewood by DAP buffer as gDNA template to RPA without another process for increase gDNA yield. Together, our method is able to detect Bx within 20 mins.