A memory device includes: a first substrate; a peripheral circuit provided on the first substrate; a first metal bonding layer provided on the peripheral circuit; a second metal bonding layer directly bonded to the first metal bonding layer; a memory cell array provided on the second metal bonding layer; and a second substrate provided on the memory cell array. A page buffer circuit in the peripheral circuit receives a verification result through the metal bonding layers, divides the verification result into stages, and sequentially outputs the verification result for the division into the stages, and a pass/failure checker in the peripheral circuit sequentially performs a counting operation about each of the stages to generate accumulated values, and compares the accumulated values and a reference value which increases from an initial value as the counting operation is performed, and the initial value is set by an external memory controller.