A series of K3B6O10Br (KBB) polar crystals have been grown along < 110 >, < 210 > and < 001 > seed directions by top seeded solution growth (TSSG) method. By optimizing the growth condition, transparent KBB crystal with the sizes of 52x29x25 mm(3) was successfully grown by using seed < 001 >-orientation from KFPbO flux. The full-width at half-maximum (FWHM) and optical homogeneity were measured as 0.0038 degrees and 3.3x10(-5) from the rocking curve and optical interferometry measurements, respectively, indicating high optical quality of the as-grown crystals. The Verdet coefficient of KBB crystal was obtained as 5.3 rad T-1 m(-1) at 635 nm by comparative method.