Provided is a catalyst layer constituting body which can prevent runoff of a proton conductive polymer from a catalyst layer even when moisture is generated by an operation of a fuel cell. In a catalyst layer constituting body of a fuel cell where catalyst particles are carried on carbon, the catalyst particles are carried on the carbon by way of a carrying layer constituted of two upper and lower layers, the upper layer of the carrying layer is formed by using a polymer having proton conductivity, the upper layer forming a proton conduction layer which conducts protons generated in the catalyst particles or protons to be supplied to the catalyst particles therethrough, and the lower layer of the carrying layer is formed using a polymer having affinity with both the proton conduction layer and the carbon, the lower layer forming an adhesive layer which bonds the proton conduction layer and the carbon to each other.