Abstract: An external pacemaker is a medical device that treats arrhythmia and facilitates cardiac pacing through electrical stimulation. The precision of its key metrics is crucial to patient safety, necessitating regular calibration. Addressing this calibration need, we developed a calibration device for external pacemakers capable of calibrating parameters such as pulse amplitude, pulse width, pulse frequency, sensing sensitivity, and refractory period. This paper presents the working principles and the design methodology of both the software and hardware of the calibration device, and the testing of its key parameters. The results demonstrate that the technical characteristics of the calibration device fulfill the calibration requirements of external pacemakers. The device, compact, user-friendly, and highly accurate, resolves the pivotal issue of the absence of a dedicated calibration device for external pacemakers. It enhances the traceability system of measurement values and contributes to lowering the clinical risk associated with external pacemakers.