The present invention relates to a method of diagnosing and treating endometrial cavity-distorting leiomyoma using microRNA, and particularly, a composition and a kit for diagnosing uterine leiomyoma, the composition and the kit including an agent capable of detecting a microRNA expression level in a biological sample; a method of diagnosing uterine leiomyoma of a subject, the method including measuring a microRNA expression level in a biological sample from the subject, and diagnosing that the subject has uterine leiomyoma having endometrial cavity distortion or uterine leiomyoma having a likelihood of developing endometrial cavity distortion, when the microRNA expression level is downregulated; and a method of treating uterine leiomyoma, the method including measuring a microRNA expression level in a biological sample from a subject, and performing uterine leiomyoma treatment when the microRNA expression level is downregulated.