Boron substitution is tried for Bi in the Sr-free Bi-2212 compound of Bi–Pr–Ca–Cu–O, and the substitution effect on superconductivity of the compound is investigated. X-ray diffraction study shows that the samples are of almost the single phase in the x range of 0.0≤x≤0.4 for the nominal composition of (Bi2−xBx)Pr0.5Ca2.5Cu2Oz. Moreover, electrical resistivity and magnetic susceptibility measurements show that the superconducting transition temperature monotonously decreases with increase of x. From these results, it is first discovered that boron is a substitutable element for Bi in the Sr-free Bi-2212 compound and that the boron substitution causes the number of hole-carriers to decrease for this compound.