Provided are: a lithium ion battery negative electrode which has high capacity and excellent cycle characteristics by suppressing separation between negative electrode active materials and separationat the interface between a negative electrode active material and a negative electrode collector; and a lithium ion battery. A lithium ion battery negative electrode which is used in a lithium ion battery, and which is characterized in that a negative electrode active material layer is formed on a negative electrode collector, said negative electrode active material layer containing a binder thathas a three-dimensional structure and a negative electrode active material that is an Si alloy configured of a eutectic structure composed of an Si phase and an Si2Ti phase.