本研究以互惠理論為基礎，探討 Instagram 摯友功能如何影響使用者看待與加自己為摯友者之間關係品質，以及是否會向對方提供社會支持，甚至是也將對方設為摯友意願。研究採線上2（被對方設為摯友與否）x2（強連結與弱連結） 實驗法，共389人參與研究。結果指出被對方設為摯友的使用者會提供對方較多資訊支持，將對方設為摯友意願也較高。而強連結會讓使用者認為有較高關係品質，並間接提供較多情緒支持與資訊支持，將他人設為摯友意願也較高。關鍵字:互惠理論、社會支持、連結強度、摯友、關係品質。 

 “Close Friend” on Instagram is a function that let users exposure their Stories to whom they want to show to. To understand reciprocity of Close Friends, this research investigated whether being the other’s Close Friends or not would affect perceived relationship quality, offering social supports and willingness to set the other to own Close Friends list. This research adopted online 2x2 experiments by manipulating two variables: whether being the other’s close friend or not and tie strength (strong ties and weak ties), and recruited 389 participants. 

Results showed that being the other’s Close Friends would make users offer more informational supports and increase their willingness to set the other into their Close Friends list. The study also showed that strong tie would increase perceived relationship quality, and indirectly make users offer more social supports and elevate willingness to set the other to own Close Friends list.