The process for the preparation of amylase inhibitor including the steps of: (A) obtaining an extract solution containing the amylase inhibitor; (B) insolubilizing the amylase inhibitor by salting out by addition of a salt or salts to the solution obtained in the step (A) and recovering the insolubilized substance resulting from the salting out; and (C) directly drying the insolubilized substance recovered in the step (B) or dissolving the insolubilized substance in water to prepare an aqueous solution, and desalting and drying the aqueous solution to recover the amylase inhibitor, whereby, an amylase inhibitor in high concentrations 0.19 AI is prepared that shows highly inhibitive activity against the amylase in high yield and with good productivity.