Coefficient of friction between bolt and wood was experimentally investigated. The friction was measured by a torque meter during the rotation of the bolt compressed by wood plates in the direction parallel to the grain. The testing parameters are contact geometry (conforming and non-conforming), wood species (Japanese cedar and SPF), contact pressure (three levels), and roughness of bolt surface (fine and coarse). The coefficient of static friction was influenced by the roughness of the bolt surface, but is scarcely influenced either by the contact geometry, the wood species, and the contact pressure. The friction associated with a heavy contact caused yielding in the wood, which reduced the coefficient of friction like incomplete friction.