I searched over the web and found the information about this. So, I tried the following. And it seems working.
1) Make a *.desktop file under the .config/autostart/ directory.
$ vi $HOME/.config/autostart/xrandr-startup.desktop
[Desktop Entry] Name=xrandr-startup GenericName=xrandr-startup Comment=Start these up at login Exec=/usr/local/bin/xrandr-startup.sh Terminal=False Type=Application X-GNOME-Autostart-enabled=true
2) Make a shell script which runs xrandr command.
# vi /usr/local/bin/xrandr-startup.sh
#!/bin/sh xrandr --output VNC-0 --mode 1280x1024
# chmod +x /usr/local/bin/xrandr-startup.sh
But some times, following dialog displayed before login.
+-------------------------- | Authentification Required | Authentification is required to create a color managed device | Password: [ ] +--------------------------
I'm not sure how to avoid this.