A copyright information embedding system is provided which is designed to embed information for copyright protection into digital audio signals without deterioration of analog audio signals reproduced. The copyright information embedding system includes an A/D converter, a modulator, a level detector, and a copyright data embedding circuit. The A/D converter converts an analog audio signal into a digital signal. The modulator modulates a copyright data signal for the digital signal using spectrum spread. The level detector detects a variation in level of the digital signal. The copyright data embedding circuit divides the copyright data signal into several codes and embeds them into the digital signal each time the variation in level of the digital signal shows a preselected variation such as a rapid rise or drop.