An image forming apparatus to check an amount of waste toner stored in a waste toner container in stages. The image forming apparatus includes a main body, a waste toner container which is installed in the main body to store waste toner, a light emitting part which emits light to detect an amount of the waste toner stored in the waste toner container, a plurality of light receiving parts which receive the light emitted from the light emitting part, and a light distribution member which distributes the light emitted from the light emitting part to the plurality of light receiving parts. Waste toner detecting regions are respectively defined on light paths between the light distribution member and the plurality of light receiving parts. The waste toner detecting regions are located at different positions along an accumulated direction of the waste toner in the waste toner container. Also, the image forming apparatus has a light path member which extends from the light distribution member such that a first end is connected to the light distribution member and a second end opposes one of the plurality of light receiving parts, thereby additionally determining whether the waste toner container is installed.