Lithium niobate (LiNbO_3) is widely known as ferroelectrics. In this study, we fabricated LiNbO_3 bicrystals with a (0001)/<112^^-0> low-angle tilt grain boundary, and investigated atomic structure of boundary dislocations by using scanning transmission electron microscopy (STEM). It was found from the observation that (0001)/<112^^-0> low-angle tilt grain boundary consists of three types of dislocations with the Burgers vector of b = 1/3[1011], 1/3[1101] and 1/3[0111]. This indicates that the combination of these three dislocations compensates the tilt angle because the discontinuity of the [0001] perfect dislocation is too large to form.
