A memory device includes a page buffer, a voltage generator, and a test controller. The page buffer is connected to a memory cell through a bit line, and is configured to sense a threshold voltage of the memory cell through a potential of a sensing node electrically connected to the bit line. The voltage generator is configured to generate a test voltage to be applied to the sensing node. The test controller is configured to control the voltage generator to apply the test voltage to the sensing node, and detect a defect of the page buffer, based on a leakage current value of the sensing node.