A data bus line control circuit prevents a problem of a data access operation on a global data bus (GDB) line although two blocks are simultaneously selected. The data bus line control circuit includes: a global data bus line which is arranged between memory units adjacent to each other as two pairs, and transmits a data from a local data bus line positioned between adjacent sub blocks; and transmission means which is connected between the local data bus line and the global data bus line, and transmits bit line signals of two sub blocks to one pair of global data bus lines different from each other through the local data bus line, when the two sub blocks are simultaneously selected by a block isolation selection signal. As a result, a circuit arrangement and a layout design become simplified, and two operations of 8K refresh and 4K refresh are possible in one chip, therefore, two kinds of effects can be achieved by one chip.