Resolution include following fixes,
1- check to see if backup folder exists or path is valid in backup location parameter
2- Finding out SQL Server Service Account
3- Check to see if SQL Server Service Account has proper access (read, write, modify) on specified location
4- If job is running under proxy account, check to see if Proxy account has permission on backup location same as above permissions.
5- If SQL Server Agent is running the job and it is T-SQL Script, it is more likely that your SQL Server Service account doesn't have permission on backup location for Access denied issue.