An image forming apparatus includes an image bearer, an optical writing unit to writing an electrostatic latent image on the image bearer, the optical writing unit including multiple optical writing elements arranged in a longitudinal direction of the image bearer and a frame to hold the multiple optical writing elements, a development device to develop the electrostatic latent image on the image bearer with developer, a developer container for containing the developer supplied to the development device, and a developer amount detector to detect an amount of developer contained in the developer container based on a light transmission amount between a light-emitting element and a light-receiving element. At least one of the light-emitting element and the light-receiving element of the developer amount detector is attached to the optical writing unit.