Gluten is a component of wheat flour and has a vital function in the manufacturing of processed food via the formation of a three-dimensional network. However, gluten is associated with several diseases, such as wheat allergy and celiac disease, and some humans with gluten hypersensitivity are not able to consume wheat products. To address this problem, not only gluten-free cereal flours but also hydrocolloids and gums as gluten substitutes are used as ingredients for gluten-free products. In this study, gluten-free breadmaking was attempted using only ripe banana flour (RBF) and wheat starch as the materials. To understand the role of RBF for gluten-free breadmaking, unripe banana was ripened and RBF was fractionated into three fractions. It was clarified that the water-soluble low molecular fraction (mainly sugars) in RBF acted as a carbon source for fermentation in the dough and the water-soluble high molecular fraction acted as a gluten substitute. Pectin in the water-soluble high molecular fraction was further analyzed for four fractions separated based on differential solvent solubility. The main pectin was chelate-soluble pectin. The RBF was shown to be a good material for gluten-free breadmaking.