Catalytic synthesis of N-isopropylacrylamide from acrylonitrile and isopropyl alcohol has been studied using a variety of solid acids in a solid-liquid reaction system at 423 K. Among typical solid and liquid acids, H-ZSM-5 exhibited an exceptionally high catalytic activity. The activity (per gain) of H-ZSM-5 increased as the Al-content (100Al/(Si + Al)%) increased and then decreased through a maximum at an Al content of 2.63%. The specific activity per one acid site, which was estimated from the initial rate and the acid amount, increased greatly as the Al content decreased, which resembles those of the hydrophobicity and the acid strength. The superiority of H-ZSM-5 activity over other strong and hydrophobic solid acids suggests the importance of the unique pore structure. While H-ZSM-5 deactivated severely during the reaction, the catalytic activities were mostly recovered by calcination at 773 K in air. IR spectroscopy and adsorption measurements revealed that the deactivation of H-ZSM-5 was mainly caused by the formation of a polymer of acrylonitrile on the catalyst surface blocking the micropores, but not limiting desorption of the product from the micropores.