Michy Batshuayi scored in the first half and Thomas Meunier wrapped up the win in the second, giving Belgium its eighth win from eight games in Group I.
The Belgians have scored 30 goals and conceded just one.
Croatia has a chance to book its place in the finals with a win in Wales, and Poland can qualify with a win over North Macedonia.
The top two teams of each group advance. The other four qualifiers will come through four tiers of playoffs in March.
Source: Fox Sports