Each signal line enters a preliminary polarity inversion period prior to a normal polarity inversion period so as to be inverted to the opposite polarity. By the preliminary polarity inversion a signal line on a border of blocks experiences a potential hike and the potential oscillates, which, however, is restored later by the application of a correct potential in the normal polarity inversion period. When transferring data per block, the problem of different potential states between the border of the blocks and an area surrounding it, which is caused by the potential oscillation of the signal line on the border of the blocks, is relieved.