An intracardiac defibrillation catheter system equipped with a defibrillation catheter 100, a power source device 700 and an electrocardiograph 800. The defibrillation catheter 100 is equipped with a first DC electrode group 31G and a second DC electrode group 32G the power source device 700 is equipped with a DC power source unit 71, a catheter-connected connector 72, an electrocardiograph-connected connector 73, an arithmetic processing unit 75 which controls the DC power source unit 71 and has an output circuit 751 for outputting a direct current voltage from the DC power source unit 71, and a changeover unit 76 in which the catheter-connected connector 72 is connected to a common contact, the electrocardiograph-connected connector 73 is connected to a first contact, and the arithmetic processing unit 75 is connected to a second contact.
