The active surface was studied by cyclic voltammogram of Platinum electrode in acidic electrolyte solution. In bulk Platinum electrode, the active surface was 2.5429x10-33 cm2. Other, in electrodeposited Platinum electrode, the active surface area was 4.85773x10-33 cm2. The both mode was similar cyclic voltammogram, but the active surface area is different value. The active surface area of electrodeposited Platinum electrode was higher than active surface of bulk Platinum electrode. However, active surface areas were error form geometric surface area of Platinum (0.053 cm2). In this experiment was highest error.