A toner supplying device for supplying toner contained in a toner container attached to the toner supplying device to a developing device of an image forming apparatus. The toner supplying device includes a toner container insertion part configured such that a toner container is inserted therein from a front side of the toner supplying device. A toner container holder that detachably holds the toner container inserted into the toner container insertion part and toner discharged from the toner container held by the toner container holder is exhausted to a toner exhaust path. A toner delivery device delivers the toner, exhausted to the toner exhaust path, to the developing device of the image forming apparatus, by mixing the toner with air. The toner supplying device includes a covering device that covers and uncovers the toner container insertion part. The covering device includes a regulating device that regulates movement of the covering device to cover and uncover the toner container insertion part. The regulating device regulates movement of the covering device to cover and uncover the toner container insertion part when toner is being discharged from the toner container held by the toner container holder in the toner insertion part and releases regulating movement of the covering device when toner is not being discharged from the toner container held by the toner container holder in the corresponding toner container insertion part.