Provided is a carbon material that can improve the cycle characteristic in charge and discharge of an all-solid-state battery. The carbon material is a carbon material to be contained in a positive electrode and/or a negative electrode of an all-solid-state battery comprising a group 1- or group 2-ionic conductive solid electrolyte, wherein in an X-ray diffraction spectrum of a mixture of the carbon material and Si in a weight ratio of 1:1, a ratio a/b is 0.2 or higher and 10.0 or lower, where a represents a height of the highest peak in the range of 2θ of 24° or larger and smaller than 28° and b represents a height of the highest peak in the range of 2θ of 28° or larger and smaller than 30°.