A developing device develops, with developer, an electrostatic latent image formed on an image carrying member, and includes a developing tank, a developer carrying member, and a drive input portion. The developing tank stores the developer and has a receiving port and a discharge port through which the developer is received and discharged respectively. The developer carrying member rotates in the developing tank while carrying the developer. The drive input portion receives a rotational force from outside the developing device and transmit the rotational force to a driven rotation shaft that is a rotation shaft of the developer carrying member. The receiving port, the discharge port, and the drive input portion are provided in the developing tank to be close to an end of the developing tank in a longitudinal direction of the developing tank.