A waste toner collecting system in an image forming apparatus which forms on the surface of an image carrier an electrostatic latent image corresponding to an original image, develops the latent image with toner and transferrs the toner image onto a copy material. The waste toner collecting system comprises a cleaning unit for removing residual toner from the image carrier after the toner image has been transferred, a container, independent of the cleaning unit, for storing the removed waste toner, and a transport device for conveying the waste toner removed by the cleaning unit to the container, with an outlet formed in the toner transport device so as to discharge the waste toner, a waste toner inlet formed in the container at a position corresponding to the outlet in the toner transport device, and shutter members provided for the outlet and the inlet, respectively, the shutter members being opened or closed according to as the waste toner container is mounted or dismounted.