The present invention is directed to improvements in or relating to designing fluid flow field bipolar plate for solid polymer electrolyte hydrogen generation by water electrolysis. Accordingly, the present invention provides fluid flow field circular bipolar plate for solid polymer electrolyte hydrogen generator, wherein said circular fluid flow field plates are each made of suitable electrically conducting material and define in a major circular surface (1) thereof a parallel open faced fluid flow channel (2) corresponding respectively to said first and second fluid flow fields; each said channel having a fluid inlet (3) at one end and a fluid outlet (4) at the other end, channel traversing a major central circular area of said surface in plurality of passes and wherein each said fluid flow field plate further includes a fluid supply opening (5) and a fluid exhaust opening (6) defined in said surface and respectively directly connected to said fluid inlet and said fluid outlet of each said channel, channel length increases gradually towards the centre of the circle and decreases from that.