A memory device that operates at high speed is provided.
The memory device includes first and second memory cells, first and second bit lines, first and second switches, and a sense amplifier. The sense amplifier comprises a first node and a second node. The first memory cell is electrically connected to the first node through the first bit line and the first switch, and the second memory cell is electrically connected to the second node through the second bit line and the second switch. The sense amplifier amplifies the potential difference between the first node and the second node. The first memory cell and the second memory cell include an oxide semiconductor in a channel formation region.