Bicrystals of Nb-doped SrTiO3, having tilt angles of 4o~18 o with respect to , were prepared by joining two single crystals at 1873 K and then investigated to identify the effect of tilt angle on the grain boundary structure. The boundaries consisted of a regular array of dislocations but the positioning of cores along the boundary was found to be changed from a line to a zigzag as a tilt angle was increased up to 10o. The 14° - tilted boundary exhibited two kinds of boundary region exist at the same grain boundary; (1) the discrete cores region as observed in 4° ~ 10° - tilted boundaries and (2) the randomly oriented region as found in the 18° boundary. Thus it was observed that the structure of low-angle tilt boundary changed from the discrete dislocation structure to the randomly oriented structure as a tilt angle increases. These structural changes at the grain boundaries are considered to be related to a minimization of strain due to the high density of dislocations.