Absorption and magnetic circular dichroism spectra of Tm3+ ions in LiNbO3 crystal have been investigated at various temperatures between 15 and 296 K, and luminescence spectra observed by excitation in various excited states of Tm3+ have been investigated in a spectral region of 400-1750 nm at room temperature. From absorption spectrum at 15 K, it is confirmed that Tm3+ ion has C-3 symmetry, indicating that they occupy Li+ and/or Nb5+ sites. The 480, 652, 780, 800, 1220, 1450, and 1650 nm emission bands were observed by excitation into the (1)G(4) State, and the 800, 1450, and 1650 nm emission bands were observed by the excitation into the F-3(2), F-3(3), and H-3(4) states, and the 1650 nm emission band was observed by excitation into the H-3(5) states. Their optical transition processes are discussed.