Abstract: A tuning device for musical instruments or voices comprises a visual stroboscopic displaying means which displays a light flow at a speed proportional to the difference of a tone to be tuned from the signal of the corresponding standard pitch. A standard pitch in a predetermined octave is synthesized from pulses generated by a high frequency oscillator the standard pitch and is divided into a pitch in a predetermined lower octave for comparing the tone to be tuned in the stroboscopic displaying means. The tone to be tuned is also divided into a signal of a pitch in the lower octave and it is transmitted to the stroboscopic displaying means.The stroboscopic display means compares the signal to be tuned with the standard signal, making a light-flow display by overlapping both the signals. The pitch and octave of the tone to be tuned is previously set on the device with a manual selector switch.