Micro-sized colloidal particles dispersed in nematic liquid crystal become topological defects in uniform orientation of liquid crystal. Since they increase the elastic energy of the liquid crystal, a long-ranged anisotropic interaction is induced between them. In this study, we reported the interparticle force measured by various methods utilizing optical tweezers. The interparticle force depends on the type of particle-defect pair and its dependence on the interparticle distance is in agreement with the theoretical prediction using electrostatic analogy. This anisotropic force enables us to construct characteristic clusters, which cannot be realized in conventional water-based colloidal dispersions. We made some novel colloidal assemblies in two dimensions by utilizing optical tweezers to demonstrate the availability of the anisotropic force in nematic colloids.