PURPOSE: To judge the quality with very high accuracy through visual inspection by comparing the good quality waveform pattern obtained previously with the processing product waveform pattern measured repeatedly every processing by means of a comparator.

CONSTITUTION: The injection speed 14 from an injection molding and injection pressure 15 are converted by means of an A/D converter 14b and 15b into A/D conversion, after that, inputted into a CPU 2. In the case where a good quality product is obtained, a good quality waveform memory switch 13 is operated and a good quality waveform pattern consisting of the injection speed 14 and the injection pressure 15 is stored in a RAM 4. AT the start of an injection, each measuring initiation 16 and 17 of the speed and pressure is performed and the measuring time in the molding period is set, and a data of the processing product inspection waveform pattern comprising the injection speed 14 and the injection pressure 15 is taken into CPU 2, and then compared with the good quality waveform pattern stored in the RAM 4. At a displaying part 6, the good quality waveform pattern and the processing product inspection waveform pattern are displayed, and in the case where if they are in the good quality zone, a waveform pattern judgement output 19 is outputted via the CPU 2.