It has been well-known that second language learners are affected by their first language when producing their L2. For speech rhythm, it has been suggested that L2 speakers are affected by L1 speech rhythm (e.g., Korean learners of English produce English without reducing the duration of unstressed vowels), and the effect is greater when speakers are beginner or intermediate-level language learners. This study, however, suggests that the direction of the effect is not always the same as researchers expected, and shows how easily speech rhythm is influenced by speech errors. The result of this study shows the relationship between the type of speech errors and speech rhythm metrics, and how that affects the perceptual proficiency of L2 speakers as well as L1 speakers. Future studies will be conducted to examine the way to infer the type of speech errors using speech rhythm metrics.