This article explores the morphological process of numeral incorporation in Japanese Sign Language. Numeral incorporation is defined and the available research on numeral incorporation in signed language is discussed. The numeral signs in Japanese Sign Language are then introduced and followed by an explanation of the numeral morphemes which are bound to root morphemes. Fourteen different paradigms are presented and, from these paradigms, two rules for numeral incorporate in Japanese Sign Language are proposed. (Contains 32 figures and 3 notes.)