A guitar is one of the most popular musical instruments. For its proper functioning every string should oscillate with a specific frequency. A process that accomplishes this is called guitar tuning. Guitar gets out of tune with time. Playing and other factors accelerate this process. Universal tuners can be of a great help in the process of guitar tuning. The peg of the tuning mechanism is however still rotated by hand. The goal of this thesis was the development of an automatic guitar tuning system where electric drive is used to turn the pegs. An Arduino microcontroller was used for this purpose. A signal from a microphone is amplified by electric circuit and send to Arduino microcontroller. After the frequency of this signal is measured, it is compared with the set value. Based on the error signal, the system tunes the string using a stepping motor.