We investigated the effect of mirin on cooked potato. Raw potato was soaked in one of the following solutions for 19 hour: water, mirin, nikiri-mirin and ethanol. The surface parts of eac soaked potato sample after boiling were then obserbed by electron microscopy. It was found that the tissue of the potato that had been soaked in the mirin solution hardly collapsed after boiling. It is considered that the tissue of the cooked potato was maintained by the effect of ethanol and glucose contained in mirin.