To analyze the H/D isotope effects on hydrogen transfer reactions in XHCHCHCHYXCHCHCHYH (X, Y=O, NH, or CH2) including the nuclear quantum effect of proton and deuteron, we propose a multicomponent molecular orbital-climbing image-nudged elastic band (MC_MO-CI-NEB) method. We obtain not only transition state structures but also minimum-energy paths (MEPs) on the MC_MO effective potential energy surface by using MC_MO-CI-NEB method. We find that nuclear quantum effect affects not only stationary-point geometries but also MEPs and electronic structures in the reactions. We clearly demonstrate the importance of including nuclear quantum effects for H/D isotope effect on rate constants (k(H)/k(D)).