The present invention relates a method for manufacturing a fuel cell. An object of the present invention is to provide a method for manufacturing a membrane electrode assembly capable of solving an electrical connection problem caused by uneven tube lengths and improving an output, and a solid polymer electrolyte fuel cell. The method for manufacturing the membrane electrode assembly of the present invention includes a seed catalyst layer forming process (1), a CNT growing process (2), a CNT entanglement promoting process (3), a catalyst carrying process (4), an ionomer arranging process (5), and a transferring (MEA conversion) process (6). According to the present invention, entanglement of adjacent CNTs can be promoted by the CNT entanglement promoting process (3) and therefore the electrical connection of the CNTs can be ensured. Thus, the output of the cell can be improved.