A membrane-electrode assembly for solid polymer electrolyte fuel cell that exhibits superior dimensional stability to high temperature of hot water generated on power generation, and that has both excellent power generation performance and durability in a low temperature environment is provided. Each of the lower electrodes is buried in a burying insulating film to have an upper surface planarized relative to the upper surface of the burying insulating film and has a plane configuration such that the distance from an arbitrary position on the upper surface of the lower electrode to the nearest end portion thereof is 0. The lower end may be provided with a forwardly projecting ledge. The light machine has a second positioning portion and an engaging portion for fixing the light bulb in a determined position when the first positioning portion of the light bulb abuts the second positioning portion.