A 79-year-old woman with systemic sclerosis was admitted to our hospital because of syncope. On admission, electrocardiogram showed progression of intraventricular conduction defect. Chest radiograph showed marked cardiomegaly. Echocardiogram revealed deterioration of left ventricular systolic function. We suspected progressive myocardial disease with Stokes-Adams attack. When we were preparing a temporary pacemaker, paroxysmal atrioventricular block with asystole for 15 seconds and convulsion occurred. Electrophysiological study showed His-ventricular block and sinus node dysfunction. A permanent pacemaker was implanted. In systemic sclerosis, progression of ventricular conduction defect may warrant prompt electrophysiological study and prophylactic pacemaker implantation.