PURPOSE: To simplify mostly check by applying a mostly defect decision in a memory chip and outputting the result of decision externally.

CONSTITUTION: A n-bit counter 2 is carrried by an exclusive OR output 43 between input data 41 to a semiconductor memory and output data 42 of a semiconductor memory by an exclusive OR circuit 1. An output signal 45 of an output latch circuit 4 latching a AND signal 44 of count outputs 21W2n of the n-bit counter 2 by the AND circuit 3 is led to an output pad 5. A mostly permissible bit number is selected by the combination of the count outputs 21W21n, and when a semiconductor memory having a defective bit number within 2 bits is decided as a non-defective memory, the AND signal 44 is selected to be AND of the count output 21 and the count output 22.