1. A data generation device configured to generate data used in a detection process using a vision sensor, based on positions of a three-dimensional model of a robot, a three-dimensional model of the vision sensor and a three-dimensional model of an object which are positioned in a virtual space, the data generation device comprising: a robot placement position designating part configured to designate a placement position of the three-dimensional model of the robot in the virtual space based on a reference coordinate system defined in the virtual space; a vision sensor placement position designating part configured to designate a placement position of the three-dimensional model of the vision sensor in the virtual space based on the reference coordinate system; a placement position storing part configured to store the placement positions of the three-dimensional model of the robot and the three-dimensional model of the vision sensor; a positional relationship calculating part configured to calculate a positional relationship between a robot coordinate system defined in relation to the three-dimensional model of the robot and a sensor coordinate system defined in relation to the three-dimensional model of the vision sensor, based on the placement positions of the three-dimensional model of the robot and the three-dimensional model of the vision sensor, without carrying out a calibration for associating the robot with the vision sensor; and a positional relationship storing part configured to store the positional relationship between the robot coordinate system and the sensor coordinate system as data used in a detection process of the vision sensor.