This experiment was carried out to investigate the effect of internal holes on the bending strength of PB. The diameters of holes are 0㎜ to 13㎜. The locations of holes are 1/8 to 4/5 point horizontally from sample end and are 1/5 to 4/5 vertically from sample surface, the numbers of holes are 1 to 4 pes. In the size of internal holes, the bending strengths of PB were decreased significantly with the increase of diameter of holes, and the relationship between diameters(D) of holes and bending strength(σb) of PB was σb=-11D+168.8 (r²=-0.99**. The effects of hole-locations and hole-numbers on the bending strengths of PB were large. and so they should be considered as major factors for the jointing design of PB. 키워드: Bending strength, particle board, internal hole