Amorphous solid electrolytes in the system Li2S-SiS2-Li4SiO4 were successfully prepared from a mixture of Li2S, SiS2 and Li4SiO4 crystals using a mechanical milling technique at room temperature. In the composition range 0 less than or equal to x less than or equal to 5 of (100-x)(0.6Li(2)S.0.4SiS(2)).xLi(4)SiO(4). conductivities of the oxysulfide powders mechanically milled for 20 h were as high as 10(-4) S cm(-1) at room temperature, which are comparable to the values of the corresponding composition of melt-quenched glasses. As the period of mechanical milling treatment was increased from 0 to 20 h, the structure of milled powders became similar to that of the glasses prepared by melt quenching. Such a structure change brought about a large conductivity increase in the resultant powders from 10(-9) to 10(-4) S cm(-1).