The present invention provides an entire solid lithium secondary battery comprising: a cathode; an anode; and a solid electrolyte layer disposed between the cathode and the anode. The solid electrolyte layer is formed of a Li(1-x)TaO3 crystal (where 0.12≦x≦0.46) having a trigonal ilmenite crystal structure. This entire solid lithium secondary battery has a good charge-discharge property.