Sodium borohydride, NaBH4, shows a number of advantages as hydrogen source for UAV PEMFC (Unmaned Aerial Vehicle Proton Exchange Membrane Fuel Cells). In order to use for UAV, the weight and volume of byproduct should be small after NaBH4 hydrolysis reaction. Therefore, the weight and volume of byproduct were studied after NaBH4 hydrolysis reaction using unsupported catalyst. The effect of catalyst type, concentration of NaBH4, concentration of NaOH and thickness of catalyst pack on the weight and volume of byproduct were studied. Most of byproduct was NaB(OH)4 and superficial volume of byproduct increased due to foam evolved from byproduct. The weight and volume of byproduct were not affected by concentration of NaOH used stabilizer. The weight of byproduct decreased as concentration of NaBH4 solution increased, but maximum volume of byproduct obtained at 23 wt% of NaBH4. Suitable defoaming agent reduced the volume of byproduct.