According to one implementation, an image processing apparatus includes the following. A setting unit sets a point in an irradiating field region of a radiation image as a reference point. A candidate point extracting unit extracts irradiating field edge candidate points based on the set reference point. A straight line candidate extracting unit extracts straight line candidates of the irradiating field edge based on the extracted irradiating field edge candidate points. A judging unit performs correct/incorrect judgment of the extracted straight line candidates. A recognizing unit recognizes the irradiating field region based on the straight line candidates judged to be correct. The judging unit calculates an evaluating value of the straight line candidates as the irradiating field edge. The judging unit performs correct/incorrect judgment of the straight line candidates based on the calculated evaluating value.
