A developing roller has a mandrel, an elastic layer and a cover layer as a surface layer. The cover layer includes a silicon oxide film containing a carbon atom chemically bonded to a silicon atom. In the silicon oxide film, the proportion of the total number of the elements of silicon, oxygen, carbon and hydrogen to the number of all detected elements, as detected with a high-frequency glow discharge light-emission surface analysis method, is 90% or more. The silicon oxide film has an abundance ratio of an oxygen atom chemically bonded to a silicon atom to silicon atoms, (O/Si), of 0.65 or more but 1.95 or less and an abundance ratio of a carbon atom chemically bonded to a silicon atom to silicon atoms, (C/Si), of 0.05 or more but 1.65 or less, and has a ratio of the maximum value to the minimum value of the (C/Si) in a thickness direction of the cover layer, of 1.50 to 33.00.