SharePoint 2013 backup from Central Administration Errors?

I have 2 Servers in one server I have installed SharePoint 2013 and in another server I have installed MS Sql server 2012 us back end for my SharePoint When I want to backup my farm from Central Administration it gives the following errors:

Object SharePoint_Config failed in event OnBackup. For more information, see the spbackup.log or sprestore.log file located in the backup directory. 
SqlException: Cannot open backup device 'F:\SPBNew\spbr0000\00000136.bak'. Operating system error 3(The system cannot find the path specified.). 
BACKUP DATABASE is terminating abnormally.

the path it gives error is actually inside my SharePoint it is fine but I don't know why it generates like this error.