In order to clarify the origin of high-conductivity layers (HCL) near the surfaces of hydrogenated diamond films, we have studied the relationship between HCL and surface structure in B-doped homoepitaxial (001) diamond films. Samples annealed in nitrogen environment at various temperatures have been characterized by Hall-effect measurements and reflection high-energy electron diffraction. It was found that HCL disappeared in the films annealed at a temperature higher than 350 degrees C, hut the (001)-2 X 1 surface-structures observed in hydrogenated films remained at 350 degrees C. This indicates that HCL is not related directly with the (001)-2 X 1 surface-structure. The origin of HCL will be discussed on the basis of the present results.