IMAGE FORMING DEVICE

PURPOSE:To perform the display of toner-empty quickly and finely to improve the convenience of use by smoothing the detecting signal of a toner residual quantity detecting sensor, and displaying a residual quantity of the toner at plural stages corresponding to levels of the smoothed signal. CONSTITUTION:The detecting output of a toner residual quantity detecting sensor 3 is smoothed by a smoothing circuit 20, and input to a CPU 14 through an A/D converter 13. When the residual quantity of the toner reduces, the detecting output of the toner residual quantity detecting sensor 3 becomes the clock oscillating signal, and this clock has dullness of the waveform in response to the residual quantity of the toner of the surface of the sensor. Consequently, a DC level of the signal smoothed by the smoothing circuit 20 has the information for finely showing the condition of toner empty. A toner residual quantity judging means 21 of the CPU 14 processes a digital value from the A/D converter 13 in a predetermined order, and judges a level thereof to inform a display unit 15 of it.