A toner path opening and closing apparatus of an image forming device includes a first shutter elastically supported by a first elastic member to open and close a first toner path, and a second shutter elastically supported by a second elastic member having an elastic modulus smaller than the first elastic member to open and close a second toner path by the first shutter. After the second toner path is opened by the first shutter, the first is opened, so that the first and second toner paths communicate with each other. The first toner path is a toner supplying pipeline to which a toner is supplied from a toner cartridge, and the second toner path is a toner injecting port disposed in a developing unit. In mounting of the developing unit, after the toner injecting port disposed in the developing unit is first opened, the toner supplying pipeline is opened, and in dismounting of the developing unit, after the toner supplying pipeline is first closed, the toner injecting port is closed, so that in mounting and dismounting of the developing unit, toner is prevented from being leaked through the toner paths.