Provided is an image processing apparatus (2000) including an index value calculation unit (2020) and a presentation unit (2040). The index value calculation unit (2020) acquires a plurality of images captured by a camera (3000) (captured images), and calculates an index value indicating the degree of change in the state of a monitoring target in the captured image, using the acquired captured image. The presentation unit (2040) presents an indication based on the index value calculated by the index value calculation unit (2020) on the captured image captured by the camera (3000).