1. An apparatus for picking up objects including a robot for picking up an object, at least one part of said object having a curved shape, comprising: a storing arrangement for storing a gray gradient distribution model of said object; a recognizing arrangement for recognizing a gray image of said object; a gradient extracting arrangement for extracting a gray gradient distribution from said gray image recognized by said recognizing arrangement; an object detecting arrangement for detecting a position or position posture of said object in said gray image in accordance with said gray gradient distribution extracted by said gradient extracting arrangement and said gray gradient distribution model stored by said storing arrangement; a detection information converting arrangement for converting information of said position or position posture detected by said object detecting arrangement into information of position or position posture in a coordinate system regarding said robot; and a robot moving arrangement for moving said robot to the position or position posture converted by said detection information converting arrangement to pick up said object.