A bolt fastening method enabling the same effect as when reducing the coefficient of friction of a thread surface without changing the coefficient of friction of the thread surface so as to realize an increase in a bolt axial force generated when fastening the bolt and a bolt fastening device realizing the bolt fastening method are provided.The bolt fastening method of the present invention is a bolt fastening method for when using a bolt having a bolt head and a bolt shank provided with an external thread to fasten fastened members, characterized by intentionally biasing surface pressures of a thread surface and a bolt bearing surface generated when fastening the bolt by imparting a lateral load parallel to the bolt bearing surface to the bolt head and, in that state, imparting a rotational torque rotating the external thread to the bolt head so as to fasten the bolt.