Abstract: A wearable device which diagnoses personal cardiac health condition by monitoring and analyzing heartbeat includes a motion sensor detecting whether the user is in a motion state; a heart rhythm sensor detecting the user's signal of heartbeat interval; a memory storing algorithm program and database for data process, comparison, and analysis; a microprocessor calculating, filtering and judging the signal of heartbeat interval; and a feedback module displaying or alarming a judgment result, wherein the wearable device continuously detects the user's motion state and heartbeat condition, and detects heart rhythm when the user is not in the motion state to further judge the user's cardiac health condition, such as atrial fibrillation.