Emission characteristics of terbium-activated $InBO_3$ under cathode-ray(c.r.) and vacuum ultra violet(v.u.v.) irradiation have been investigated as a functions of norminal compositions and firing conditions. From the x-ray analysis, it was found that some of the synthesized samples contained excess $In_2O_3$ and the amount of the excess $In_2O_3$ varied with the norminal composition and heat treatment conditions. The samples with remanent excess $In_2O_3$ showed lower luminescence intensities than the ones free of excess $In_2O_3$. The phosphors of norminal composition of $InBO_3+10mol%B_2O_3:2mol%Tb$ synthesized at $1250^{circ}C$ showed excellent CL and PL properties.