PURPOSE: To have certain display of the working time from commencement of processing by judging a command in order to clear the accumulated value of the working time stored in the program, and by accumulating the working time after clearing the accumulated value.

CONSTITUTION: If the accommodation data in an input memory 104 is a command for count clear, a control part 105 emits a reset signal CRS to clear the content in a counter 106, in which the working time is accumulated, and also generates a start signal CST to set a flip-flop 107. As a result, an AND gate 108 opens to allow input of pulses with a certain period of cycle into said counter 106, and after commencement of accumulation of working time, the control part 105 makes a data read device 102 read the data of next block to be followed thereafter by usual NC processing. When processing of the work proceeds and, now, a command to indicate program end or tape end is read from a tape 101, the control part 105 emits a stop signal CSP, and the counter 106 finishes counting the working time upon resetting the flip-flop 107.