Each of bit lines BL and source lines SL is pre-charged to power source voltage VDD before read-out of data. At the time of read-out of data, only in a selected memory cell column, a corresponding source line SL is coupled to a data bus line DB, while a corresponding source line is driven to ground voltage VSS. In non-selection memory cell columns, each of bit lines BL and source lines SL is keptat the power source voltage VDD. As a charge/ discharge current is not caused in bit lines BL corresponding to the non-selection memory cell columns which does not contribute directly to read-out of data, power consumption at the time of read-out of data can be reduced. To reduce power consumption of a MRAM device formed of magnetic memory cells having magnetic tunnel junctions.