A machining liquid is supplied to a predetermined level when a workpiece is on a table. A volume of the workpiece is obtained from a difference between the machining liquid amount at the predetermined level when a previous workpiece is not on the table, and the machining liquid amount when the workpiece is on the table. A weight of the workpiece is obtained from the obtained volume and a previously stored density of the workpiece. A weight of a mounting jig is obtained in the same procedure. A total volume of the jig and workpiece is obtained when the jig is on the table and the workpiece is fixed to the jig. The volume of the workpiece is obtained by a difference with respect to the volume of the jig. The weight of the workpiece fixed to the jig is obtained from the obtained volume and the previously stored density.

The micro-electric discharge milling machine includes a base having an X-axis guide plate mounted thereon, allowing for movement in the X-direction. A Y-axis guide plate is mounted on the X-axis guide plate, allowing for movement in the Y-direction. A dielectric bin is located on the Y-axis guide plate and is movable in the X-direction and the Y-direction via the X-axis guide plate and Y-axis guide plate, respectively. A workpiece platform is located within the dielectric bin for securing a workpiece. A vertical plate with a Z-axis guide plate extends from the base. A drill chuck is mounted on the Z-axis guide plate for securing a rotating electrode. A spark control circuit controls a location of a spark generated by the rotating electrode with respect to a surface of the rotating electrode.

The micro-electric discharge milling machine includes a base having an X-axis guide plate mounted thereon, allowing for movement in the X-direction. A Y-axis guide plate is mounted on the X-axis guide plate, allowing for movement in the Y-direction. A dielectric bin is located on the Y-axis guide plate and is movable in the X-direction and the Y-direction via the X-axis guide plate and Y-axis guide plate, respectively. A workpiece platform is located within the dielectric bin for securing a workpiece. A vertical plate with a Z-axis guide plate extends from the base. A drill chuck is mounted on the Z-axis guide plate for securing a rotating electrode. A spark control circuit controls a location of a spark generated by the rotating electrode with respect to a surface of the rotating electrode.

A simulated current generation unit is connected in series to a power supply device for an electric discharge machine in a state in which a contact and a contact are in contact with each other and generates a simulated current (I.sub.sim) for simulating current caused by dielectric breakdown of a discharge gap constituted by a workpiece and a pipe electrode, which face each other with a predetermined gap in order to perform electrical discharge machining of the workpiece by a narrow-hole electric discharge machine, based on an applied voltage of the power supply device for an electric discharge machine. An NC device judges the presence or absence of an abnormality of the power supply device for an electric discharge machine based on the simulated current (I.sub.sim) detected by a current detection unit.