I had used indentation guides and uninstalled it because the indentation lines are not align correctly. After I removed the plug-in, however, the vertical lines(i guess it is kind of indentation guides) appear like a screenshot. So, I reinstall and uninstall the plug-in but they remain same.
Oh! Your advice works! When I turned off Outliner plug-in, the lines disappeared. So I checked options of the plug-in. I found “Draw vertical indentation lines” function is the problem. I turned off the function and the vertical lines disappear but the other functions work well. Thanks!