A developing device comprising: a developing roller; a toner; and a toner supply roller that supplies the toner to the developing roller, the developing roller comprising: an electro-conductive substrate (21, 22), and a surface layer on the electro-conductive substrate (21, 22), the surface layer being composed of a single layer, wherein the surface layer has a matrix comprising a crosslinked urethane resin as a binder, when an elastic modulus of the matrix in a first region in a cross section in a thickness direction of the surface layer is defined as E1, the first region being from an outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface, an elastic modulus of the matrix in a second region in the cross section is defined as E2, the second region being from a position at a depth of 1.0 μm from the outer surface to a position at a depth of 1.1 μm from the outer surface, and E1 and E2 are measured as specified in the description, E1 and E2 satisfy following relational expressions and: E1 ≥ 200 MPa 10 MPa ≤ E2 ≤ 100 MPa wherein fine particles are attached to the outer surface of the surface layer, and the fine particles form protrusions on the outer surface of the surface layer; each of the fine particles comprises an organosilicon compound, and in a cross-sectional view of each of the fine particles and the outer surface of the surface layer, each of the fine particles has a substantially flat surface that is in surface contact with the outer surface of the surface layer and a curved surface that constitutes at least a part of each of the protrusions; a number-average value of the longest diameter w of the substantially flat surface of the fine particles is 10 nm to 400 nm as calculated by the method specified in the description; the toner comprises a toner particle and silica particles as an external additive; the toner particle comprises a binder resin; and an adhesion rate of the silica particles to the toner particle measured by a water washing method as specified in the description is 50% or more. a developing roller; a toner; and a toner supply roller that supplies the toner to the developing roller, an electro-conductive substrate (21, 22), and a surface layer on the electro-conductive substrate (21, 22), the surface layer being composed of a single layer, wherein the surface layer has a matrix comprising a crosslinked urethane resin as a binder, when an elastic modulus of the matrix in a first region in a cross section in a thickness direction of the surface layer is defined as E1, the first region being from an outer surface of the surface layer to a position at a depth of 0.1 μm from the outer surface, an elastic modulus of the matrix in a second region in the cross section is defined as E2, the second region being from a position at a depth of 1.0 μm from the outer surface to a position at a depth of 1.1 μm from the outer surface, and E1 and E2 are measured as specified in the description, E1 and E2 satisfy following relational expressions and: E1 ≥ 200 MPa 10 MPa ≤ E2 ≤ 100 MPa wherein fine particles are attached to the outer surface of the surface layer, and the fine particles form protrusions on the outer surface of the surface layer; each of the fine particles comprises an organosilicon compound, and in a cross-sectional view of each of the fine particles and the outer surface of the surface layer, each of the fine particles has a substantially flat surface that is in surface contact with the outer surface of the surface layer and a curved surface that constitutes at least a part of each of the protrusions; a number-average value of the longest diameter w of the substantially flat surface of the fine particles is 10 nm to 400 nm as calculated by the method specified in the description; the toner comprises a toner particle and silica particles as an external additive; the toner particle comprises a binder resin; and an adhesion rate of the silica particles to the toner particle measured by a water washing method as specified in the description is 50% or more.