In order to realize a total-solid lithium ion secondary battery having high performance, a solid-state lithium ion conductor having high ionic conductivity and low electronic conductivity is obtained. The solid-state lithium ion conductor is characterized by containing: Li, P, and S; and at least one metal element selected from Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Re, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Zn, Cd, and Hg.