A memory device includes a first sense amplifier, and a second sense amplifier. During a read operation, a first signal based on a first output of the first sense amplifier corresponding to data stored in a memory cell before writing reference data therein and a second signal based on a second output of the first sense amplifier corresponding to data stored in the memory cell after writing reference data therein, are supplied to the second sense amplifier, which compares the first and second signals to output a comparison result representative of the data stored in the memory cell. During a test operation, a third signal based on the first output and a fourth signal based on an output from a voltage supply circuit are supplied to the second sense amplifier, which outputs a comparison result of the third and fourth signals as a test result.