PURPOSE: To correspond to a sweep having inclination over a wide range, by preliminarily forming a reference sweep table and generating a desired sweep step signal on reference to said table.

CONSTITUTION: An operational processing circuit 2 is an operational processing part for performing operation calculating top, last and clock, and the sweep start voltage, sweep end voltage and sweep interval necessary for the operation of top, last and clock are inputted from the input apparatus provided on the side of a main controller by an operator to be inputted to a measuring unit through a driver. The top, last and clock calculated by the circuit 2 are stored in an execution table 3 under the control of a control circuit 4. When a trigger order is inputted from a main controller, the circuit 4 successively generates a sweep step signal while refers to a data table 1 on the basis of the parameter of the execution table 3. This value is converted to an analogue value by a digital/analogue converter circuit 5 to be given to an object to be inspected.