An aspect of the present disclosure discloses a method for diagnosing a network performance in an apparatus for diagnosing network performance connected to a switching device provided between a first entity and a second entity. The method may include: obtaining at least one mirrored packet for at least one packet transmitted between the first entity and the second entity based on mirroring from the switching device, calculating performance related indicator representing performance of a network service associated with the first entity and the second entity based on at least a part of information included in the at least one mirrored packet, and storing the calculated performance related indicators.