PURPOSE: To drive a section word line pulsative without slowing down the speed of a low decoder low in operation speed and reduce power consumption and improve high speed capacity by driving pulsatively a selection signal line instead of a main word line when combining a double work line system and an automatic power down system.

CONSTITUTION: NOR gates 46 are provided between output ends of each selection signal SS and a section decoder 45, and a signal of corresponding output end of the section decoder 45 is supplied to an input end, and a reverse signal 'WA of an activation signal WA is inputted in a parallel to another input end. After changing of address, a main word line MWL is selectively driven by a low decoder 41 according to the address. Similarly, after changing of the address, the selection decoder 45 drives selectively only one output end corresponding to the address. Thus, only one NOR gate 46 is operated, and a selection signal line SS to which the output end is connected is driven pulsatively.