Developing cartridge

A developing cartridge, comprising:

• a casing configured to accommodate developer and having a first side and a second side oppositely arranged in a first direction, the casing having a third side and a fourth side oppositely arranged in the second direction, the first direction and the second direction being intersected with each other;
• a developing roller rotatable about a first axis extending in the first direction, and being positioned at the third side;
• a coupling being positioned at the first side, and for receiving driving-force to rotate;
• a detected part movable according to rotation of the coupling, at least a part of the detected part being positioned at the second side;
• and
• a driving surface being inclined to the first direction, and including a first driving surface and a second driving surface,
• wherein there is a first angle between the first driving surface and a base surface perpendicular to the first direction, and a second angle between the second driving surface and the base surface, and the first angle is greater than the second angle.