The purpose of this study is to clarify the colloquial sentence final ending ‘-ulkel’ has polysemy between Epistemic-Event modality and to discuss the meaning and syntactic characteristics of ‘-ulkel’. When a sentence can be interpreted with more than two meanings, it has polysemy. ‘-ulkel’ can express the two meanings: Speculation and Regret. While there is less argument that ‘-ulkel’ belongs to Epistemic modality when it has the meaning of Speculation, it is controversial what modal category ‘-ulkel’ belongs to when it has the meaning of Regret. This study critically reviewed preceding literatures on the modality and analyzed syntactic and modal meanings of ‘-ulkel’. Through this process, it is revealed that the Regret meaning of ‘-ulkel’ is affiliated with Event modality when the subject(usually speaker) was able to control the state of affairs in the past. A speaker expresses Willingness to control the state of affairs in the past when ‘-ulkel’ is used as Event modality. However, it is impossible for the present speaker to control the state of affairs in the past. This is the reason why the speaker regrets. Also, the meaning of Regret may arise as a result of unreal conditions and speculation and, in this process, ‘-ulkel’ has Epistemic modality. When ‘-ulkel’ is used as Epistemic modality, it represents probability and has a meaning of speculation based on integrated knowledge. The results of this study can be used to establish the meaning of ‘-ulkel’ of Regret which has not been unified until now, and to prove the relation between Epistemic-Event modality.