We propose a model of molecular motor based on diblock copolymer strongly adsorbed on a patterned surface. One of the blocks of the copolymer is modeled as field responsive. It is shown that time-periodic collapse-readsorption of the responsive block leads to the directed motion (reptation) of the molecule along the "track" provided by the surface pattern. Both the Langevin dynamics (LD) technique of computer simulation for the bead-spring model and numerical solution of the Newton equations of a simplified (toy) model of the copolymer are used. The physical reason of directionality of the motion is shown to be an anistropy of the friction of the molecule with the surface.