Hydrogen trapping states in pure aluminum foils with 99.99% purity with different amount of blisters have been investigated by means of thermal desorption spectroscopy. Three peaks are seen in the spectra, where the amount of hydrogen from the third peak at the highest temperature range increases with increasing in the volume fraction of the blisters. Hence, the third peak is revealed to arise from the hydrogen in the blisters. The desorption energy of hydrogen released from the blisters is 76.3 kJ/mol. On the other hand, the first peak is inferred to be due to the hydrogen diffusing with vacancy, considering the diffusion distance of the vacancy as well as untrapped hydrogen atom.