PURPOSE: To test an integrated circuit in the AND/OR system or the like by an external control of a random distribution converter to make the probability outputting a specified theoretical value in a test pattern distributing in a recessed pattern with respect to the weight axis.

CONSTITUTION: A random number distribution converter 12 responding to a uniform random number generator 10 is controlled by a parameter α from an external equipment 11 and the geometry of the appearance probability distribution of a logic value is changed freely with conversion function units 13 and 14. Consequently, the probability of outputting a specified theoretical value from a test pattern generator 15 controlled by the equipment 11 can be made to distribute in a recessed pattern with respect to the weight axis. As compared with the binomial distribution control or the like, the test pattern corresponding to the distribution probability of a specified logic of an equipment to be tested can be formed quickly and accurately thereby enabling the testing of an integrated circuit in the AND/OR system or the like for a shorter time.