This study aims to: first, understand the current learning status of idiomatic expressions in Korean Sign Language(KSL) through the analysis of KSL textbooks published up till now by KSL Professional Institute, and secondly, propose a list of KSL educational idiomatic expressions. Accordingly we examined past literature and analysed KSL textbooks. As a result of the literature review, we identified that idiomatic expressions in KSL are not distinguished from modification of sign and polysemy. This is seen in the criteria of narrow sense of idiomatic expressions, that asserts more than one linguistic signs are not employed as a mere sum of meanings. This means that the modifications of signs and polysemy, both of which do not comply with the formal criteria of idiomatic expressions, are considered as idiomatic expressions. Next, as a conclusion of analysis of KSL textbooks, there were only three books which explicitly covered idiomatic expressions. Even the textbooks that introduced idiomatic expressions manifestly presented one word as idiomatic expressions, thereby violating the formal criteria for idiomatic expressions, defined as "phrases of two or more words." As per the time period when KSL idiomatic expressions were taught, they were introduced in basic level KSL textbooks, unlike the awareness that the idiomatic expressions were to be educated in advanced level; in few numbers though. We have also identified the phenomenon that the KSL idiomatic expression were few in narrow sense and more in the broad sense. Thus, we propose a list of KSL educational idiomatic expressions that includes both narrow and broad senses.