1. An object picking device, comprising: a camera adapted to capture a two-dimensional image including an image of a plurality of the same kind of objects that are randomly piled; a robot adapted to pick the objects one-by-one from the plurality of objects; an image processing part which processes the image captured by the camera; and a handling controlling part which controls the robot, wherein the image processing part comprises: a target detecting part which detects information of the two-dimensional position and the size of each objects in the image of the plurality of objects; a data storing part which stores height information regarding the height of the existing position of an object at a reference position, the height information being associated with size information of the object in the captured image at the reference position, the data storing part also storing data regarding a feature model of the object; a target selecting part which selects an object as a target to be picked, the object having the highest degree of priority which is calculated by using at least one of size information of an image of each detected object, a degree of coincidence between the image of the detected object and the feature model, and a degree of inclination of the image of the detected object in relation to the feature model; a view line direction calculating part which calculates the direction of a view line of the camera in the three-dimensional field between the camera and the selected object, based on the information of the two-dimensional position of the selected object; a target position estimating part which calculates the existing height of the selected object based on the size information of the selected object and the information of the exiting position and the size of the object at the reference position stored in the data storing part, the target position estimating part further calculating the three-dimensional position of the selected object based on the existing height of the selected object and the direction of the view line; and a grip correction calculating part which calculates an amount of correction of the movement of the robot, the amount of correction being adapted to grip the selected object by using the robot, wherein the handling controlling part comprising: a movement controlling part which controls the movement of the robot, so as to move a robot hand to the three-dimensional position of the selected object, along the direction of the view line of the camera in relation to the selected object; a contact sensing part which detects that the robot hand has come in contact with the selected object; a grip commanding part which commands the robot hand to stop the movement thereof and grip the selected object with the robot hand when the contact sensing part detects the contact between the robot hand and the selected object; and a pull-out commanding part which commands the robot to pull out the object gripped by the robot hand.