A display device for guitar tuners and a method of displaying the tuned states of guitar strings. The method is performed such that the control unit performs control so that the backlight emits light having a predetermined color by turning on the backlight when a tuner is turned on, and then performs control so that the backlight emits light having a different color when the tuning of guitar strings is completed using the display device, which includes a Liquid-Crystal Display (LCD) panel provided in an equalizer mounted to a guitar body, and configured to display the tuned states of the guitar strings, a backlight mounted behind the LCD panel, and a control unit configured to control the LCD panel and the backlight.