You Do Need power plug adapter while traveling from Spain to San Marino.

Here is Why You Need An Adapter

The outlet and plug type used in San Marino are C, F and L and in Spain are C and F. This is how they look like.

Spain

In Spain, outlets of type C and F are in use.

Type C

Type F

San Marino

In San Marino, outlets of type C, F and L are in use.

Type C

Type F

Type L