An image forming apparatus includes an image bearing member for bearing a latent image, a developer carrying member for developing the latent image with a developer, a developer accommodating portion for accommodating the developer, and a detecting device including a light emitting element and a light receiving element for detecting a remaining developer amount in the developer accommodating portion. In addition, a stirring member stirs the developer by rotating in the developer accommodating portion. The stirring member is rotated in a first period in which the stirring member crosses an optical path of light from the light emitting element toward the light receiving element and a second period in which the stirring member does not cross the optical path of the light. The stirring member is rotated at a first rotational speed in the first period and is rotated at a second rotational speed in the second period higher than the first rotational speed, and wherein the first period and the second period are included in one rotation of the stirring member.