The efficiency of working memory capacity for 6 year-old children was measured with the use of a listening span test. Two types of listening span tests and memory span test were conducted to 73 preschool children. Listening span test 1 (LST1), which was based on the reading span test developed by Daneman & Carpenter (1980), required subjects to listen to a set of unrelated sentences and recall the first word of each sentence after listening to all the sentences. In listening span test 2 (LST2), a set of semantically related sentences was used. The largest set size for which the subject could recall was defined as the listening span. The correlation between the score of LST1 and LST2 was found to be significant. Moreover, correlation between memory span and the score of LST1 was shown to be high.