Among additive-manufacturing methods, selective laser sintering (SLS) is promising from the viewpoints of quality and precision. In this study, copolymer PBT (cPBT) powder with 30-wt%-added short glass fiber (SGF) was used to investigate the influence of anisotropy in the build plane on characterization of composite cPBT materials. The mechanical properties (tensile strength, flexural strength, and notched Charpy impact strength) of SLS specimens arranged in the X-direction (roller-movement direction) or Y-direction (direction perpendicular to the surface of the specimens) in the build plane were evaluated. In the case that the SLS specimens were aligned in the Y-direction, the mechanical properties decreased by 10‒16% compared with those values of the specimens aligned in the X-direction. These results confirm that the influence of fiber orientation is a significant factor in determining the mechanical properties of SLS-formed products. Moreover, in the case the SLS specimens were aligned in the Y-direction, compared to cPBT specimens without added SGFs, cPBT specimens with added SGFs show lower tensile strength and flexural strength, but higher impact strength. This result is supposed to be due to the fact that fiber orientation is the main factor affecting impact strength; in contrast, higher porosity of cPBT with added SGFs compared to that of cPBT only and low adhesion of cPBT and SGFs decrease the tensile strength and flexural strength. Comparing heat-deflection temperatures (HDT) of cPBT SLS specimens with added SGFs revealed that in the case the specimens were aligned in the Y-direction, HDT is 117.5 ℃, which is 33.2 ℃ lower than HDT in the case the specimens were aligned in the X-direction. However, that HDT is considerably higher than that in the case of cPBT without added SGFs (i.e., 69.6 ℃). In other words, even if anisotropy of SGFs is taken into account, the effect of adding SGFs on HDT is significant.