PURPOSE: To automatize selecting action in the next process of a robot by additionally providing a weight measuring function, and deciding weight so as to select the action in the next process, in the industrial robot for performing such as work of taking out a product.

CONSTITUTION: In a process of inserting an insert ring 12 to a product 4 manufactured by, for instance, a die-cast machine 7, the product 4 is clamped by a product gripper 3, in a robot 1, to measure weight of this product by a measuring sensor 2. This measured weight is compared with total weight of the product 4 and the insert ring 12, to decide whether the insert ring 12 is provided or not and whether a weight error is permissible or not. When a weight difference from the basic weight is in a permissible range, the product is set to a trimming metal mold 10, and when out of the range, the product is input to an inferior product discharge conveyer 5.