Mean energy losses of 10.4-MeV neutral hydrogen atoms penetrated through thin carbon foils of 3.7-13.4 mu g/cm(2) were measured using a high-resolution magnetic spectrograph. The measured particles are those entered into the carbon foil as H-0 and emerged from it as H-0. From the attenuation measurement of H-0 in the foils, we can regard the energy losses as those of H-0 in a frozen charge state. The measured stopping power of carbon for 10.4-MeV H-0 is 21.3+/-1.8 eV/(mu g/cm(2)) and is about one-half that for H+ at the same speed. This result agrees well with the theoretical predictions based on the first-order Born approximation.