As a diverse range of smartphones has been recently developed, the use of smartphones is being dramatically increased. The use of smartphones allowed many tasks to be done at smartphones, which used to require the use of computers. Especially, along with the increase in smartphone use, the users of SNS (Social Network Service) also have been sharply increased. The SNS saves a variety of information such as exchanged pictures and videos, voice mails or location sharing, chat history, etc. as well as simple user data, so that the acquisition of data that are useful in the aspect of digital forensic is achievable. This thesis reviews the types of SNS that are available for the iPhone, a recent example of highly used smartphones, and studies the data to be collected by client and the analysis methods accordingly.