Pine wood nematode (PWN), Bursaphelenchus xylophilus is associated with the pine wilt disease and transmitted by pine sawyer, Monochamus alternatus. Because pine sawyer has one-year life cycle, one natural infection of PWN is occurred a year. Therefore, artificial propagation method of PWN is needed to improve experiment associated with PWN. In this study, effect of diameter, paraffin sealing of twig and dosage on pine wood nematode reproduction in Japanese black pine, Pinus thunbergii. PWN reproduction was compared in twigs of P. thunbergii and P. densiflora. Numbers of reproduced PWN were higher with decreasing diameter of twig. Distance (5 and 10 cm) from inoculation site of PWN did not influence reproduction of PWN. Reproduced numbers of PWN were higher in the paraffin-sealing twig than non-sealing twig. Dosage of PWN influenced reproduction of PWN. Reproduction rate was the highest at the rate of 10 IJs (13.7 and 61.1-fold increasing in P. densiflora and P. thunbergii, respectively 30 days later) whereas lowest at the rate of 1000 Ijs (1.1 and 0.7-fold increasing in P. densiflora and P. thunbergii, respectively 30 days later). Numbers of reproduced PWN were more in P. thunbergii than P. densiflora.