Maranta arundinacea L., also known as arrowroot, are underground rhizomes, or tubers from which arise reed-like, erect stemmed plant. This can be considered as a non-conventional raw material for flour. In Bustos, Bulacan, history tells that arrowroot starch is the primary ingredient of its chief town product which is Minasa, a local biscuit. In the process of extracting starch from the arrowroot, the waste rhizome is collected and grinded as arrowroot flour. This paper seeks to probe the ash content, moisture content, crude fat, crude protein and carbohydrates present on the arrowroot flour. In the proximate analysis it showed that the waste rhizome flour contains 2.03% ash, 8.15% moisture, 0.36% crude fat, 1.86% crude protein and 87.6% carbohydrates. Based on the result, it implies that the rhizome waste product of the arrowroot starch extraction can be made as a flour and can have a potential of producing products that may increase the value of the production of arrowroot in the town of Bustos in Bulacan.