A cell structure for a fuel cell stack that is formed by stacking unit cells C each including a membrane electrode assembly 1 and a pair of separators 2 holding the membrane electrode assembly 1 therebetween. The membrane electrode assembly 1 includes a frame 3 in the periphery having such a size as to extend outward over the edges of the separators 2. Communication holes 21, 22 in communication with the front and back sides are formed in the frame 3 in an area from a sealing part 11 between frames 3 adjacent in the cell stacking direction to a sealing parts 12 between the membrane electrode assembly 1 and the separators 2. The air in a space Q formed between the inner and outer sealing parts 11, 12 is allowed to be released to the outside through the communication holes 21, 22, and a breakage of the adhesive of the sealing parts 11, 12 is thereby prevented.