C15 Laves RFe2 (R= Y, Ce, Sm, Gd, Tb, Dy, Ho and Er) compounds were thermally analyzed to elucidate conditions of hydrogen-induced amorphization (HIA), i.e. amorphization of intermetallics by hydrogen absorption, using a pressure scanning differential calorimeter (PDSC) in a hydrogen atmosphere of 1.0 MPa. As the temperature increases, hydrogen absorption in the crystalline state, HIA, precipitation of RH2 in the amorphous phase and decomposition of the remaining amorphous phase into RH2+oc-Fe occur exothermally for RFe2 (R=Y, Sm, Gd, Tb, Dy and Ho). HIA and precipitation of ErH2 occur simultaneously in ErFe2. On the contrary, hydrogen absorption of CeFe2 always leads to HIA, i.e. no hydrogen absorbed crystalline phase is formed. The mechanism of HIA in the C15 Laves phases RFe2 is discussed on the basis of the experimental results.