Four　new　homoverrucosane-type　diterpenes　(1-4)　and　two　known　analogs　(5-6)　were　isolated　from　the　marine　sponge　Halichondria　sp.　Their　structures　including　absolute　configurations　were　determined　by　combination　of　spectroscopic　analyses,　theoretical　calculations　and　comparison　with　data　of　literatures.　The　cytotoxicity　against　human　multiple　myeloma　cell　line　RPMI-8266　of　compounds　1-4　was　evaluated,　but　none　showed　activity　(IC50　＞　10　mu　M).　It　was　the　first　report　that　homoverrucosanes　isolated　from　the　marine　sponge　Halichondria　sp.　(C)　2020　Published　by　Elsevier　Ltd.