The pressure of compressed hydrogen changes with temperature when mass and volume are constant. Therefore, when a compressed-hydrogen tank is filled with a certain amount of hydrogen it is necessary to adjust the filling pressure according to the gas temperature. In this study, we conducted hydraulic pressure-cycle tests to investigate the fatigue life of Type-3 compressed- hydrogen tanks when environmental temperature and filling pressure are changed. The results indicated that the fatigue life at low temperatures (-40C, 28MPa) and room temperature (15C, 35MPa) was almost equal. However, the fatigue life at high temperatures (85C, 44MPa) was shorter than that under other conditions, suggesting that stress changes caused by thermal stress affect the fatigue life of the Type-3 tank.