Picosecond time-correlated single-photon-counting studies have been made on the electronic excitation migration among positively charged porphyrins, TAPP (5,10,15,20-tetrakis(4-trimethylammonio)phenyl)porphyrin, tosylate) and ZnTMPyP (zinc 5,10,15,20-tetrakis(1-methyl-4-pyridinyl)porphyrin, chloride), adsorbed on a negatively charged surface of DHP (dihexadecyl phosphate) vesicles and its trapping at porphyrin aggregates (dimer or higher associates). The observed fluorescence decay curves cannot be reproduced by decay functions derived assuming single-step transfer from porphyrin monomer to nonfluorescent aggregate uniformly distributed in two dimensions or three dimensions. The decay function for the case of single-step transfer derived on the basis of the fractal theory is also unable to reproduce the results. It has been confirmed that the fluorescence decay function derived for multistep excitation migration on fractal and fast trapping at the first trap encounter can reproduce satisfactorily the observed results, and the fracton dimension relevant to porphyrin monomer distribution on the vesicle has been estimated to be 1.65.