A novel memory device is provided. Over a driver circuit layer, N memory layers (N is a natural number greater than or equal to 2) including a plurality of memory cells provided in a matrix are stacked. The memory cell includes two transistors and one capacitor. An oxide semiconductor is used as a semiconductor included in the transistor. The memory cell is electrically connected to a write word line, a selection line, a capacitor line, a write bit line, and a read bit line. The write bit line and the read bit line extend in the stacking direction, whereby the signal propagation distance from the memory cell to the driver circuit layer is shortened.