The disclosure relates to a 5G or 6G communication system to support a higher data transmission rate. The disclosure relates to a reconfigurable intelligent surface (RIS) enabling a low phase error at various incidence angles/reflection angles and an apparatus including the same. The RIS comprises a unit cell pattern formed in a direction corresponding to a polarization direction, the unit cell configured to adjust a reflection phase; a switch operably connected to the unit cell pattern, the switch configured to adjust the reflection phase; and a dummy pattern positioned between unit cell patterns in case that a plurality of unit cells is arranged.