PURPOSE: To provide a tester wherein, in addition to a static-characteristic test, also a test by a periodic signal can be made automatically and without labor.

CONSTITUTION: In a setting operation, a procedure wherein a voltage whose level is changed stepwise and a periodic signal are generated is programmed in a memory 19 from a setting part 21. In a measuring operation, the voltage whose level is changed stepwise and which is superposed on the peirodic signal is output from a signal generation circuit 15 including a periodic-signal generation circuit 14 under the control of a CPU 16. A test signal which is output is taken into the CPU 16 via a signal measuring circuit 11 and an A/D converter 12.