The purpose of this study was to examine the reliability and validity of a Japanese short form of the Swanson Cognitive Processing Test, which assesses capacity of working memory. Test-retest reliability was acceptable (r = .76). Concurrent validity was suggested through comparison of scores on the Reading Span Task (r = .55). Means on the Japanese short form were comparable with means for the 3 subtests for the older group and 2 subtests for the younger group. With the exception of the Auditory Digit Sequence, results suggested that both the Japanese short form and the initial Swanson Cognitive Processing Test measured comparably the working memory in the two samples of children.