Numerical control device and logging methods

Diagnostic information in the vicinity of the timing of occurrence of abnormality for efficiently obtaining, numerical controller, when detecting the occurrence of a predetermined event (S3, Yes), previously with reference to diagnostic information that changes successively articles diagnostic information in the development of elephant is detected timing obtained as the reference value, by using the reference value and generates a start condition by making the set processing advance (S4), sequential change to diagnostic information starts when the condition is met (S2, Yes), starts the logging process sequential changing diagnostic information (S5).