Abstract: A low toughness workpiece cutting apparatus, a low toughness workpiece manufacturing method and a low toughness workpiece manufacturing program for predicting an occurrence of defect and/or non-occurrence of defect before a cutting process of low toughness material. A defect prediction device is provided with a storage device, a processor and an interface. The storage device stores tool data that represent physical characteristics and a shape of a tool, cutting data that represent a group of parameters of a cutting process to be performed to a workpiece by use of the tool and material data that represent physical characteristics and a shape of the workpiece. The processor performs an analysis of deformation of the workpiece due to a cutting force and an analysis of fracture due to the deformation, and performs a prediction of an occurrence of defect and/or a non-occurrence of defect of the workpiece due to the cutting process.