Developing device

A developing device comprising:

• a developer bearing member which bears developer including toner and carrier to develop an electrostatic latent image formed on an image bearing member;
• a developing container which accommodates the developer;
• a conveying screw which conveys the developer accommodated in the developing container;
• and
• an inductance sensor which includes a detecting portion which detects magnetic permeability of the developer accommodated in the developing container,
• wherein the inductance sensor has such detection sensitivity that the detection sensitivity with which the detection portion detects magnetic permeability in a state where a magnetic material is disposed at a position 1 mm away from the detection portion in a vertical direction is equal to or greater than 10% of detection sensitivity with which the detection portion detects magnetic permeability in a state where the magnetic material is disposed at a position which is in contact with the detection portion,
• wherein the conveying screw includes:
• a rotary shaft;
• a blade which is spirally formed on an outer circumference of the rotary shaft;
• and
• a rib formed as to protrude outwardly from the outer circumference of the rotary shaft,
• wherein the rib is disposed opposite the detection portion with respect to the conveying direction of the conveying screw, and
• wherein the rib is provided with a magnet.