The present invention relates to an apparatus and method for processing a surface of a substrate by subjecting the surface to successive surface reactions of a first and second precursor. The apparatus includes a nozzle head having two or more precursor nozzles and a moving mechanism for moving the nozzle head in non-linear oscillating movement in a first and second movement direction between a first extreme position and a second extreme position via a center position. The moving mechanism includes first driving means for accelerating the nozzle head in the first moving direction and decelerating the nozzle head in the second moving direction and second driving means for accelerating the nozzle head in the second moving direction and decelerating the nozzle head in the first moving direction.