PURPOSE:To measure automatically the real hardness of a body to be measured which has large variance in hardness obtained by averaging the surface hardness and center hardness by providing a detection part consisting of a load cell and a contactor to the vacuum sucker of an automatic cake elevating machine. CONSTITUTION:The contactor 3 of the load cell fitted to the vacuum sucker 1 of the automatic cake elevating machine 8 of a filter press is inserted into a cake 4 which is sucked by the sucker 1 and an object of hardness measurement, and the load cell 2 detects the load. At this time, the insertion depth of the contactor 3 into the case 4 is so determined that its tip is nearby the center part of the cake regardless of its hardness. Then, an electric signal which is obtained by the load cell 2 corresponding to the load at the time of the insertion is supplied to an arithmetic control part 5. The arithmetic control part 5 performs specific arithmetic to decide whether or not the load is at the prescribed upper or lower limit of the hardness, outputs the result to a cake hardness recording part 6 and a display part 7, and controls the automatic elevating machine 8 according to the result to sort normal and defective cakes.
