Graham Williams will transfer to the post of director at the Mid and West Wales Regional Office of the NHS with effect from 19 June.
'We would like to thank Graham for his strong commitment to supporting local authorities to drive forward social services improvement, his policy developments and his effective working relationships with the WLGA over recent years.
'Graham's background in local government gave him key insights into the delivery of social services and in his role as chief inspector. He has been a champion of social services improvement and hugely influential in supporting the local authority drive for increased performance. He has also played a vital role in the recent establishment of the Social Services Improvement Agency for Wales.'
'I am sure everyone in local government will want to join me in wishing Graham well in his new role.'
Mr Williams has held the post of chief inspector at the Social Services Inspectorate for Wales since March 1999.
--The Social Services Improvement Agency (SSIA) for Wales is based at the WLGA and will work on behalf of local authorities to increase the pace of improvement and excellence within social services.
--The funds available to the agency in any year are provided from health and social services within the Assembly division.