A method for detecting heart rhythm irregularities, including the steps of: measuring pulse peaks continuously over a period of time to obtain pulse peak sequence and pulse peak time interval sequence corresponding to the pulse peak sequence; and calculating the absolute value of a difference between a single pulse peak time interval in the pulse peak time interval sequence and an average value of the pulse peak time interval sequence, and determining that an irregular pulse peak (IPP) has occurred if the absolute value is larger than or equal to 15% to 25% of the average value of the pulse peak time interval sequence. A detection device using the method is also provided. This uses a non-invasive approach to detect heart rhythm irregularities such as sick sinus syndrome, irregular pulse peaks, irregular heartbeat, and atrial fibrillation, and can be applied to a sphygmomanometer or a wearable device.