Is pacemaker the same function as defibrillator?

No: Pacemakers just treat slow heart rhythms. Defibrillators can act as a pacemaker but can also treat fast dangerous heart rhythms by speeding up the heartbeat to interrupt the abnormal circuit (painless) or shocking the rhythm back to normal as a last resort. If a shock is needed it can hurt a lot for a few seconds but in most cases this is worth it because the device is saving your life.

No.: Both defibrillators (icds) and pacemakers can treat slow heart rhythms. Some pacemakers can perform anti-tachycardic pacing, which can terminate some upper-chamber tachycardias. For the most part, however, tachycardias can not be treated by a pacemaker - and implantable cardioverter-defibrillator is required.