An object is to move a rail molecule by means of a biomolecular motor deposited on a base and inactivate the biomolecular motor through irradiation with light having a predetermined wavelength, to thereby readily and reliably fix the rail molecule at a predetermined position, while orienting the rail molecule in a predetermined direction without employment of any reagent. A method for fixing a rail molecule which has polarity and on which a biomolecular motor moves in a direction corresponding to the polarity includes depositing a biomolecular motor on a base； moving a rail molecule by means of the biomolecular motor； and inactivating the biomolecular motor by irradiating the biomolecular motor with light having a predetermined wavelength when the rail molecule reaches a predetermined position, to thereby fix the rail molecule so that it is oriented in a predetermined direction.
