A cellulose fiber can reduce environmental burden while providing an enhanced modulus of elasticity easily and reliably. A composite material contains the cellulose fiber. A method of producing the cellulose fiber includes preparing a solution where needle-shaped phases each comprising a cellulose I crystal structure are dispersed in a matrix phase comprising a cellulose II crystal structure. The cellulose fiber includes the matrix phase and the needle-shaped phases contained in the matrix phase and the needle-shaped phases are oriented along an axial direction.