In this paper, we present a technique for measuring the value of charge-to-mass ratio in toners using a newly developed apparatus in which charged toner particles are transported above a periodic array of conductors driven by four-phase rectangular pulses. At the end of the flow path of toner particles in the transport system, parallel electrodes are set up for sensing charge-to-mass ratio. The sensed input signal is amplified by differential amplifier and is converted to digital values. By analyzing the sensed signal, the value of the ratio for the charged toner particles can be calculated. This technique can measure easily the mean value and its distribution under coditions of on-line use. We find that the distribution shows a good correspondence with the result of the E-Spart method near the peak range.