To reduce the number of sampling inspections and the number of workers at the same time and to automate operation.

A shape precision diagnosing device for a work is provided with a detecting means 7 to detect, for example, vibration generated during processing by a processing system 1 or the effective power of a motor for a machine tool for the processing system 1 and a moving average processing means 10 is provided to output the time series pattern of a detecting signal consisting of a waveform not containing high frequency noise effecting moving average processing through input of a detecting signal. By effecting computation processing by a neutral net work based on the processing time series pattern, corresponding to the processing time of a work, of the time series pattern, a neuro-computing means 16 is provided to output an estimated value of shape precision of a work.