In a fuel cell, perimetric portions of each sheet body, an upper support member, and a lower support member are sealed against one another by a seal that includes first and second seal portions. The first seal portion is of glass having a softening point lower than a working temperature of the reactor and seals against the upper surface of the perimetric portion of the sheet body and the lower surface of the perimetric portion of the upper support member as well as against the lower surface of the perimetric portion of the sheet body and the upper surface of the perimetric portion of the lower support member. The second seal portion is of glass having a softening point higher than the working temperature and seals against the lower side end and upper side end of the perimetric portions of the upper and lower support members, respectively.