PURPOSE: To improve the quality and reliability of a work in a work quality controlling method and its device in a press machine.

CONSTITUTION: Pressing signals of a pressure sensor 3 in a press machine are inputted into a computer 5 having a neural net-work device 6, a recording device 7 of the computer displays that the work is normal or defective and together a controller connected to the computer operates and controls the press machine. Loading wave shape pattern of a normal products wave shape group of the work or a defective products wave shape group and the operational characteristics of a neural circuit net of wave shape understanding and the operation controlling information of the press machine 1 are inputted into the neural net-work device 6 while learning, the computer 5 calculates the loading wave shape pattern matching to the operational characteristics following passing of time during operating based on learning of the neural net-work device 6, the controller a operates ana controls the press machine 1, the recording device 7 displays judging the normal/defective quality, and the operation is stopped at the time displaying that it is defective.