ASSEMBLY DEVICE

PURPOSE:To make it possible to detect early a defect position in an assembly device adapted to be used for manufacturing a semiconductor device, by comparing the condition of a sensor during operation with the condition of the same when it is at an operation reference position so as to self-diagnose the operating condition of the device. CONSTITUTION:In a condition in which the entire device normally operates, the operation is detected by sensors A, B, C, at the respective positions of the latter with a predetermined cycle period. If the sensor A arranged lateral of a disc 6 fails so that the sensor A does not operate even though the disc 6 is located at the original position, a control section 17 reads the conditions of the sensors A, B, C at the original point which are previously stored in memory. That is, at the original point, the conditions of the sensors A, B, C should be such that the sensor 4 lateral of the disc 6 is in its detecting condition while the sensor B at one of movable jigs 15 is in its detecting condition, and the sensor C at the other movable jig 15 is in an undetecting condition. Accordingly, the control section judges that either the sensor A or a motor 3 fails, and displays the defect position.