A transfer belt unit for use with an image forming apparatus includes: a transfer belt; and a belt memory. The transfer belt is configured to transfer toner on a photosensitive drum of the image forming apparatus onto a sheet conveyed to a portion between the photosensitive drum and the transfer belt. The transfer belt is also configured to make contact with a cleaning roller of the image forming apparatus and to be cleaned by the cleaning roller. The belt memory includes: a first storage area configured to store therein a first rotation time period indicating a total of a period of time that the cleaning roller rotates at a first rotational speed; and a second storage area configured to store therein a second rotation time period indicating a total of a period of time that the cleaning roller rotates at a second rotational speed faster than the first rotational speed.