Provided are a rat-eye bean extract improving blood glucose control and bioactivity, which is produced from rat-eye beans as health food so as to be able to improving storability, portability and potability, and a method of producing the same. The rat-eye bean extract is produced by putting rat-eye beans, which are cleanly washed without foreign materials and are soaked in water for five hours, and water into a steam pot at a volume ratio of 3:1 along with rice straw, fermenting water, which is boiled to steam the rat-eye beans in weak flames for five hours, in a hot-floored room for two to three days, putting the fermented water and a grapefruit juice into the steam pot at a weight ratio of 99:1, and heating a mixture of the fermented water and the grapefruit juice in a closed state at a temperature of 110 to 120° C. for four to five hours.
