PURPOSE: To perform load monitoring suitable to working behavior by comparing an actual stroke pressure by an abnormality detecting means with a stroke pressure diagram selected by a diagram selective means to detect an abnormal state of a press and notifying the abnormal state to the outside based on an output signal from the malfunction detecting means.

CONSTITUTION: The angle of rotation of a crank shaft 1 is detected 6. The pressure in a hydraulic room of a slide 5 is detected by a hydraulic pressure detecting means 7. An actual load value is detected 10 based on the maximum and minimum of the detected hydraulic pressure. An inputted angle of rotation and an actual load value are opposed to each other and stored 20. Plural kinks of stroke pressure diagrams ar stored 30. The actual stroke pressure is compared by the abnormality detecting means 50 with the stroke pressure diagram selected by a diagram selective means 40 to detect the abnormal state of the press. The abnormal state is notified to the outside through a notifying means 60 based on an output signal from the abnormality detecting means 50. In this way, a load monitor easy of handling and wide in applicability can be offered.