In a high-porosity CBN vitrified grinding stone having a homogeneous structure, a CBN abrasive grain, a large-diameter inorganic hollow filler having an average particle diameter in a range from a grain size one class coarser to a grain size one class finer with respect to a class indicating a grain size of the CBN abrasive grain, and a small-diameter inorganic hollow filler having an average particle diameter of ⅕ to ½ of that of the CBN abrasive grain are bonded by an inorganic bonding agent.