The phase stability of the amorphous phase against electron irradiation and the crystallization behavior under electron irradiation were investigated in Zr-Cu based metallic glasses. The phase stability of the amorphous phase against thermal crystallization, i.e., thermal stability was evaluated by the temperature range of supercooled liquid region (ΔT_x). The ΔT_x values for Zr_66.7Cu_33.3, Zr_65.0Al_7.5Cu_27.5 and Zr_65.0Al_7.5Ni_10.0Cu_17.5 alloys were 54K, 89K and 119K, respectively. The amorphous phase of Zr-Cu based metallic glasses was not stable under electron irradiation. The crystallization of fcc-Zr₂Cu phase was accelerated by electron irradiation instead of bct-Zr₂Cu phase which appeared during thermal annealing. The increase in the thermal stability of the amorphous phase is effective for the decrease in the crystallization rate under electron irradiation, but not always effective in suppressing the occurrence of electron irradiation induced crystallization.