A fingerprint sensor device and an operation method thereof are provided. The fingerprint sensor device includes a driving electrode, a driving circuit, a fingerprint sensing plate, a reading circuit and a determination circuit. The driving circuit applies a driving signal to an object through the driving electrode. The fingerprint sensing plate has sensing electrodes configured to sense the object. The reading circuit reads the driving signal through the fingerprint sensing plate. During a period between a rising edge time point and its adjacent falling edge time point of the driving signal, the reading circuit respectively samples the driving signal in at least two different phases to obtain at least two sampling results and outputs a difference value of the at least two sampling results. The determination circuit checks the difference value to determine whether the object to be sensed is a real finger or a fake finger.