The present invention provides a machining state checking apparatus and method for checking whether a workpiece mounted on a machine tool and a workpiece fixture are shifted. A machining state checking apparatus has an actual CCD camera for imaging a workpiece fixed on a machine tool and a workpiece fixture and generating actual two-dimensional image data thereof, a virtual image generating section for generating virtual two-dimensional image data of the workpiece and workpiece fixture based on data on three-dimensional models of the workpiece and workpiece fixture, a comparing section for comparing the actual two-dimensional image data and virtual two-dimensional image data generated by the actual CCD camera and the virtual image generating section, respectively, and determining whether they match each other by comparing the portions corresponding to the workpiece and workpiece fixture in the actual two-dimensional image and the virtual two-dimensional images of the workpiece and workpiece fixture.