An image forming apparatus includes a buffer configured to temporarily store in the buffer toner supplied from a toner cartridge and to be fed to a developing unit; a magnetic reed switch configured to sense magnet variation occurring in a sensing range and sequentially output signals each indicating a result of the sensing; a toner level indicator plate disposed within the buffer to swing up and down about a fixed edge in response to a change in a level of the toner that remains in the buffer, the toner level indicator plate having a magnet on a free edge thereof, the magnet being made to reach the sensing range in a state where the toner level indicator plate has swung down.