IMAGE PROCESSING DEVICE, PROGRAM, IMAGE PROCESSING METHOD, COMPUTER-READABLE MEDIUM, AND IMAGE PROCESSING SYSTEM

An image processing device 20 acquires a plurality of captured images obtained by imaging a sample including a target cell at a plurality of different focal distances, sets an object region for detecting the target cell in at least two of the plurality of captured images, and performs determination about whether or not the target cell is included in the object region based on whether or not an image feature quantity based on change in image information in an image in-plane direction and a focal distance direction of an image in the object region in the plurality of captured images satisfies conditions defined for the target cell.