An image processing apparatus includes: an image acquisition unit that acquires a plurality of endoscope images obtained by imaging an observation target at different times with an endoscope; a blood vessel extraction unit that extracts blood vessels from the plurality of endoscope images; a blood vessel index value calculation unit that calculates a blood vessel index value for each of the blood vessels extracted from the endoscope images; a temporal change calculation unit that calculates a temporal change of the blood vessel index value; a determination unit that determines a state of a mucous membrane of the observation target using the temporal change of the blood vessel index value; and a monitor that displays a determination result of the determination unit.