Image forming apparatus

An image forming apparatus, comprising:

• an image carrying member that includes a photosensitive layer formed on a surface thereof;
• a charging device that charges the surface of the image carrying member to a prescribed surface potential;
• an exposure device that applies light to the image carrying member charged by the charging device so as to form thereon an electrostatic latent image with attenuated electrostatic charge;
• a developing device that includes a developer carrying member carrying a two-component developer containing a magnetic carrier and toner and develops, into a toner image, the electrostatic latent image formed on the surface of the image carrying member;
• a toner container that contains the toner with which the developing device is to be replenished;
• a toner concentration sensor that detects a toner concentration which is a ratio of the toner to the magnetic carrier in the developing device;
• a toner charge amount detection portion that detects a toner charge amount which is a charge amount per unit mass of the toner in the developing device;
• and
• a control portion that controls, based on a result of detection of the toner concentration by the toner concentration sensor, replenishment of the developing device with the toner from the toner container,
• wherein
• based on the toner charge amount detected by the toner charge amount detection portion, the control portion executes first target value changing control of changing a target value of the toner concentration.