The method of forming a carbon layer by vapor phase deposition starts a film deposition process of the carbon layer after a surface to be coated with the carbon layer is heated while adjusting a partial pressure of moisture in a film deposition system of the carbon layer to 5×10−6 Torr or less. This carbon layer forming method by means of a vapor phase deposition technique such as sputtering ensures that a high-quality carbon layer having high adhesion to the lower layer and significantly reduced pinholes or cracks is obtained.