Developing device, process cartridge, and image forming apparatus including a holder which has projections within a hole accomodating a developer regulator or a developing roller

A developing device for developing a latent image formed on an image bearer, the developing device comprising:

• a developing roller to carry developer;
• a developer regulator of a round-bar shape facing the developing roller to regulate an amount of the developer carried on a surface of the developing roller;
• and
• a holder having:
• a first hole in which an end of the developer regulator is inserted;
• a second hole in which a shaft at an end of the developing roller is inserted;
• and
• a first projection and a second projection on an inner circumferential surface of at least one of the first hole or the second hole, the projections protruding toward an inside of the at least one of the first hole or the second hole,
• the holder holding the end of the developer regulator and the shaft,
• wherein the first projection and the second projection are disposed at substantially equal distances from an imaginary line connecting a hole center of the first hole and a hole center of the second hole when viewed in a cross section orthogonal to an axial direction of the developing device.