Lithium insertion characteristics of a complex oxide containing V(V), beta-Cu2V2O7, were investigated. Lithium insertion was carried out chemically using an n-BuLi/hexane solution. The valence states of copper or vanadium and the structural changes after lithium insertion were analyzed by ESR and XRD measurements, respectively. It was revealed that reduction processes occurred successively with an increasing extent of lithium insertion, x = Li/2 (V + Cu). Up to x = 2, Cu (II) was reduced preferentially to Cu(I), and Cu (I) and a half of V (V) were reduced to Cu (0) and V (IV), respectively at 2 < x. Preferentiality is predominant for beta-phase oxide than for alpha-phase oxide.