A solid polymer electrolyte composite for an electrochemical reaction
apparatus that possesses satisfactory ion conduction properties and has
excellent mechanical strength and heat resistance, is provided. The solid
polymer electrolyte composite is characterized in that a solid polymer
electrolyte is contained in the continuous pores of an expanded porous
polytetrafluoroethylene sheet which has continuous pores and in which the
inner surfaces defining the pores are covered with a functional material
such as a metal oxide. An electrochemical reaction apparatus containing
an electrolyte, wherein said electrochemical reaction apparatus is
characterized in that the aforementioned solid polymer electrolyte
composite is used as this electrolyte is also provided.