This paper introduces the new cavitation tunnel constructed at the University of Tokyo. Its unique feature is the controlability of cavitation nuclei distribution through filters as well as an electrolysis nuclei generator of hydrogen bubbles. A hemispherical-nosed axisymmetric body was tested in this cavitation tunnel for a given nuclei distribution and the number and size of the traveling cavities on the body were compared with calculated results. With the present numerical approach, the results of the calculated and observed cavity size distribution are in qualitative agreement.