To provide a leadless cardiac pacemaker configured to perform leadless pacing.

A cardiac pacing system 100 includes a leadless cardiac pacemaker 102 that contacts electrically with a cardiac muscle 104 of a heart chamber, is implanted, and is composed to perform leadless pacing. The cardiac pacemaker 102 has an electrode, and communicates with an external device 105 by the conduction communication signal conducted from the electrode through the living tissue of a patient.