A structure is provided which reduces erroneous estimation when a state of a work is estimated. An image processing apparatus includes: a camera which inputs an image of a work; a work state estimation unit which estimates a state of the work from the image which has been input by the camera; an occurrence probability storage unit which stores an occurrence probability that is previously associated with each state of the work; and a reliability calculation unit which calculates reliability for the estimated state of the work, based on the state of the work estimated by the work state estimation unit and the occurrence probability which corresponds to the state of the work.