Developing apparatus having regulating blade with specific surface properties, process cartridge and image forming apparatus

A developing apparatus comprising:

• a developer bearing member configured to bear a developer;
• and
• a regulating member configured to come in contact with the developer bearing member, and regulate a thickness of a layer of the developer borne on the developer bearing member, wherein
• 3≤Rz<20(μm),
• 30≤Sm≤100(μm), and
• Vmp≥0.05 ml/m2 are satisfied
• where Rz represents a maximum height roughness, and Sm represents an average interval of unevenness in a portion of a surface of the regulating member that comes in contact with the developer bearing member, and Vmp represents a volume in an initial state of a protruding peak part in a three-dimensional surface roughness defined in ISO 25178.