The infiuence of hydrogen on the magnetic structures in thulium was determined by measuring the temperature dependence of the low field magnetization over the temperature range from 4.2 to 90 K. Results show that the magnetic ordering temperatures decrease with increasing hydrogen concentrations up to the limit of simple solubility of 7.7 at. ％H. The magnetization curves for the samples up to 5.2 at. % H show the thermal hysteresis in the ferrimagnetic region. On the basis of the indirect exchange theory, the hydrogenation effects for the density of states at the Fermi energy are discussed.