1. An image processing apparatus which positions a first image and a second image with respect to each other, the image processing apparatus comprising: a first elasticity information acquiring unit configured to acquire first elasticity information regarding elasticity of a subject in the first image; a second elasticity information acquiring unit configured to acquire second elasticity information regarding the elasticity of the subject in the second image; and a positioning unit configured to position the first image and the second image with respect to each other on the basis of at least one of the first elasticity information and the second elasticity information.