javascript code appears in headers

Hi I have multiple websites with wordpress and I am facing problem. I am scanning my cpanel and found all header files of wordpress websites are infected. I removed the code from header files manually and saved it and after that I scanned I files again then virus was disappear. But It coming back on next day. I am removing that code again but same thing after one day its coming back.

I tried following things

1. tried changing password.
2. tried fresh installation and dump old database.

but still same issue the header file compromised again.
please help me someone.

site link is jiyagroup.org

regards
Santbeer