This study investigated the effects of the proton-exchanging conditions of the sulfonated poly (ether ether ketone) (sPEEK) membranes on the decal transfer rate. Various pre-treatment conditions of proton-exchanging the sPEEK membranes were used in terms of the acid concentration, temperature and time. The sPEEK membranes were analyzed to examine the effects of the acid concentration, temperature, and immersion time. The proton conductivities of the membranes were evaluated. The membrane electrode assembly, (MEA) of sPEEK membranes were fabricated by the decal transfer method. As a result, the pre-treated sPEEK membranes showed the highest proton conductivity (0.044 S cm ^-1 , 0.16 meq g ^-1 ) immersed in 0.5 M H₂SO₄ for 2h, and it brought about the highest cell performance (0.39 A cm ^-2 @ 0.6 V, 0.269 W cm ^-2 ) due to a decrease in Ohmic resistance. Among the conditions for pre-treatment, the concentration of the pre-treatment acid solutions was found to be the most significant factor determining the proton conductivity of the membranes.