You Do Need power plug adapter while traveling from Equatorial Guinea to Niger.

Here is Why You Need An Adapter

The outlet and plug type used in Niger are C, D, E and F and in Equatorial Guinea are C and E. This is how they look like.

Equatorial Guinea

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

Type C

Type E

Niger

In Niger, outlets of type C, D, E and F are in use.

Type C

Type D

Type E

Type F