To improve processing efficiency and yield by monitoring a set state of a vessel storing workpieces and monitoring operation of a carrying means for selecting and taking out the workpieces in the vessel.

A processing device provided with a carrying mechanism 4 for carrying out and in wafers W selected from the vessel 6 storing a plurality of the wafers W and a processing part 3 for performing processing on the wafers W is provided with a cassette sensor 7 for detecting presence of the vessel 6, a timer function for detecting an operation state of the cassette sensor 7, and CPU 8 driving on the basis of signals from the cassette sensor 7 and the timer function. In the case that the vessel 6 is not present or in the case that setting of the vessel 6 is not normal or in the case that malfunction of the cassette sensor 7 is detected, the state is displayed with an alarm 9, after the vessel 6 is set at a prescribed position on the basis of the display, the wafers W in the set vessel 6 are selected with a mapping sensor 18, and abnormal operation of the carrying mechanism 4 is detected to transmit the detection signals to CPU 8.