You should disable "System Integrity Protection" which is a new feature in El Capitan.
First, you should run the command for rootless config on your terminal
# nvram boot-args="rootless=0"
# reboot
Then, you should run the command below on recovery partition's terminal (Recovery OS)
# csrutil disable
# reboot
I've just solved my problem like that. I'm not sure that the first part is necessary. Try as you like.
--WARNING
You should enable SIP again after everything works;
Simply reboot again into Recovery Mode and run in terminal
# csrutil enable