A replay mode control device in which the replay mode in reproducing music or video contents is controlled so as to be suitable for a user. A headphone of a mobile music reproducing device is provided with a vibration sensor for detecting movements of the user in the up-and-down direction. A walking movement detection unit detects the walking interval of the user based on an output of the vibration sensor. A replay mode controller manages control to adjust the replay rate of music contents to the walking interval of the user.