Diabetes is one contributing factor towards the increasing of arterial stiffness. A contour analysis of photoplethysmogram(PPG) pulse with diminished dicrotic notch caused uncertainty measurement. Therefore, area under curve of PPG (auc-PPG) was proposed to overcome this problem. Auc-PPG was compared for two different levels of HbA1c which are HbA1c<8% (Group 1) and HbA1c>10% (Group 2). Auc-PPG was found to be significantly higher among diabetic subjects with HbA1c<8% than among those with HbA1c>10%. The auc-PPG could be a parameter that indicates the hardening of arteries associated with HbA1c levels.