Visa is required for citizens of Belgium to visit Vietnam. Belgian nationals may have 2 options: Visit Vietnam embassy in Belgium (Brussels) or apply for a visa on arrival to Vietnam from Belgium online. Belgian citizens may apply for both tourist and business visa to Vietnam for the stay of 1 to 6 months from Belgium. Please check this link for visa fee for Belgian citizens.

All the information for getting a visa from Vietnam embassy in Belgium can be found here: http://www.vietnamembassy.be