Abstract: X-ray diffraction pattern of Bi₄(SiO₄)₃ was recorded with F₃₀=158.90 using a conventional x-ray diffractometer. Atom positions and displacement parameters of Bi, Si and O in Bi₄(SiO₄)₃, were determined by Rietveld analysis using those data. R_wp is 11.8. The cubic cell parameter is 1.02867(5)nm. It was found that the SiO₄ tetrahedra is a distorted one; two of the O-Si-O angle are 107.13° while the other two are 114.26°. The structure was reported in detail. The reason for this distortion is attributed to the lone-pair-electron 6s² of Bi³⁺ ion.