What is the name of agency which oversees accredited education institutions?

There isn't one single agency that oversees *all* accredited education institutions worldwide. Accreditation is a regional or national process. The agency depends on the country and sometimes even the state or province within a country.

For example, in the United States, there are several regional accrediting agencies, such as the Higher Learning Commission (HLC), WASC Senior College and University Commission (WSCUC), and the Southern Association of Colleges and Schools Commission on Colleges (SACSCOC), that accredit colleges and universities. There are also specialized accreditors for particular types of institutions or programs.

To find the accrediting agency for a specific institution, you would need to check the institution's website. The information is usually readily available.