How can I get a duly certified copy of my diploma? Can the translation of degree be certified by a notary or must it be certified only by "apostille". Or both?

The copy or translation of the degree must be duly certified by the Belgian Embassy or Consulate General of your home country. For countries where the Hague Legalization Convention applies, certification may also be done by "apostille", to be delivered by the competent authority. For further information on which countries fall under the Hague Convention, please consult: http://www.hcch.net/index_en.php?act=conventions.authorities&cid=41  

When your diploma is certified in one of the above-mentioned ways, you do not need to get it certified again by a notary. Alternatively, if you have a notary's certification, it will be acceptable insofar that the Convention confirms the notary to be a competent authority for diploma certification in your home country. Please note: all degrees which are not in Dutch, English, French or German need to be officially translated into English.