You Do Need power plug adapter while traveling from Belgium to Lebanon.

Here is Why You Need An Adapter

The outlet and plug type used in Lebanon are C, D and G and in Belgium are C and E. This is how they look like.

Belgium

In Belgium, outlets of type C and E are in use.

Type C

Type E

Lebanon

In Lebanon, outlets of type C, D and G are in use.

Type C

Type D

Type G