PURPOSE: To reduce the memory capacity of a pattern memory greatly by sorting test patterns and storing as serial data, and specifying the start address of a pattern for every pin of an LSI and taking a test.

CONSTITUTION: The pattern memory 4 is stored with all test patterns while all the test patterns are divided to specific length and the same patterns are unified. The start addresses of patterns which are divided and stored in the pattern memory 4 corresponding to respective input pins are registered in a pattern base address file 5. A bit counter 7 specifies the depth of the patterns and an adder 8 adds a base address from the pattern base address file 5 to a counted value from a bit counter 7 to access the pattern memory 4. The output of the pattern memory is set as data on all input pins by a shift register and latch 9 to generate a pattern.