Activated carbons were successfully employed for the support material of catalyst in the DMFC. By re-activation process, activated carbons, which have various surface areas and porosities, could be obtained. In the present study, Pt–Ru/AC700 showed the best catalytic activity of 18 mW=cm2 in the air breathing-type DMFC single cell test. By combination of I–V curves and XRD analysis, it was revealed that more closely Pt dispersed catalysts have better catalytic activity. But as the inner-metal distances became closer the peak activity point occurred. The optimum catalys tcondition obtained in this study is suggested as the Pt particle size of 1:68 nm with inter-particle is 2:59 nm.