The surface roughness (graininess) of a globular molecule of ovalbumin in aqueous buffer solutions was investigated through data from small-angle x-ray scattering in the Porod region. The scattering intensity I changes according to I = K1q−4 or I = K1q−4 + K2. Here q is the wave vector, and K1 and K2 are constants. This means that the surface of the globular molecule does not have a fractal structure, but the electron density transition is relatively sharp at the interface. The specific inner surface Os of the native globular molecule is approximately 1.7 times that of a sphere with a smooth surface. The value of Os is almost independent of the ovalbumin concentration and pH values, but increases with heat denaturation of the system.