a voltage of a bit line connected to a memory cell is stepped up up to a power supply voltage by a precharge circuit . before data is read from the memory cell , the voltage of the bit line is stepped down to a voltage level lower than the power supply voltage by a step - down circuit . a precharge switching element controls a connection between a high - potential - side power supply and the precharge circuit and a connection between a low - potential - side power supply and the precharge circuit . a power supply connecting circuit is provided between the precharge switching element and the high - potential - side power supply . a ground connecting circuit is provided between a connecting point at which the precharge switching element is connected to the power supply connecting circuit and the low - potential - side power supply .