A method for detecting the three-dimensional structure of a log comprises the operating steps of: making the log (2) rotate axially, leaving it free to translate during the rotation; during said rotation repeating the step of detecting the relative surface structure of the log (2) at least at one log surface portion (13), so that the relative surface structure of substantially all of the points of at least the log (2) lateral surface is detected at least once; and combining the relative surface structures detected to reconstruct an overall surface structure for at least the log (2) lateral surface, the detection steps being carried out in such a way that each detection step result shares at least several points with at least one other detection step result, while the step of combining the relative surface structures is carried out in such a way that the shared points are made to coincide with each other.