Electrochemical performance of the Li2S-P2S5-Cu composite materials was examined in all-solid-state lithium secondary batteries. The 80Li(2)S center dot 20P(2)S(5) (mol.%) solid electrolyte with the addition of Cu was partially used as an active material with lithium source in all-solid-state cells. The initial discharge capacity of 110 mAh g(-1) (normalized by the weight of 80Li(2)S center dot 20P(2)S(5)-Cu), which corresponds to 400 mAh g(-1) (normalized by the weight of Li2S), was obtained in the cell using the 80Li(2)S center dot 20P(2)S(5)-Cu composite electrode with the molar ratio of Li2S/Cu = 48/52. Cycling performance and reaction mechanism of the electrode in the solid-state cell were investigated.