Hydrogen retention properties of isotropic graphite, B 4 C converted graphite, SiC converted graphite and tungsten were evaluated by using a technique of thermal desorption spectroscopy after the hydrogen ion irradiation (5 keV, H + 3 ) in an ECR ion source. The ratios of retained hydrogen at RT were 32, 56 and 110 for B 4 C, SiC and tungsten, respectively, and B-H or Si-H bond in the thermal desorption spectrum. Tungsten had also two peaks in the range below 1000°C. In the annealing temperature dependences of the retained hydrogen, the ratios of retained hydrogen for tungsten, B 4 C and SiC more rapidly decreased with the temperature, compared with the case of graphite. In order to reduce the hydrogen retention, the helium ion irradiation (5 keV, He + ) and the subsequent thermal desorption experiment were conducted after the hydrogen ion irradiation. The reductions of the hydrogen amount for tungsten and B 4 C were larger than that of isotropic graphite. However, the reduction for SiC was smaller, compared with the case of isotropic graphite.