Disclosed is a storage device comprising a positive electrode material containing graphite; a negative electrode material containing an oxide of at least one metal element selected from Ti, Zr, V, Cr, Mo, Mn, Fe, Co, Ni, Cu, Zn, Sn, Sb, Bi, W and Ta, which may preferably contains a metal oxide containing at least Ti as a metal element; and an electrolyte solution. This storage device has high capacitance and high discharge voltage, thereby having high energy. Consequently, this storage device can have high energy density, while being excellent in cycle performances and rate performances.