Crystal structure of sugilite has been refined by the least squares method using 435 reflections measured on an automated single crystal diffractometer using MoKα radiation. The final unweighted R-factor is 0.047 for 429 reflections. The cell dimensions are: a=10.007(2), c=14.000(2)Å; space group P6⁄mcc. Sugilite is isostructural with milarite group minerals, and can be described as (K_0.81Na_0.19)^[12] (H₂O_0.91Na_0.64)₂^[9] (Fe³⁺_1.32Na_0.59Ti⁴⁺_0.06Fe²⁺_0.03)₂^[6] (Li_2.12Al_0.59Fe³⁺_0.29)₃^[4]Si^[4]₁₂O₃₀ with Z=2 by structure formula of milarite group defined by Forbes, Baur and Khan (1972). The SiO₄ tetrahedra from hexagonal double rings with the composition Si₁₂O₃₀. These double rings are linked by Li, Al and Fe³⁺ atoms in tetrahedral four-coordination to form a tetrahedral frame structure. Na and H₂O are located in nine-coordinated sites.