Greater than two orders of magnitude improvements in the absolute frequency and isotope shift measurements of the In⁺ 5S^{2 1}S₀(F=9/2)－5s5p ³p₁(F=11/2)transition near 230.6 nn are reperted. The fourth-harmonic of a semiconductor laser is used as the light source. The absolute frequency is measured with the help of a frequency comb referenced to a Cs atomic clock. The resulting transition frequencies for isotopes ¹¹⁵In⁺ and ¹¹³In⁺ are measured to be 1299648954.54(10)MHz and 1 299 649 585.36(16)MHz,respectively. The deduced cooling transition frequency difference is 630.82(19)MHz. The isotope shift is calculated to be 695.76(1.68)MHz.