PURPOSE: To provide a measuring instrument for coverage ratio of address space for which a measuring result can be easily obtained.

CONSTITUTION: This instrument is comprised of an input means 12 which designates a symbol 24, an address correspondence means 13 which obtains the leading address 23a and the final address 23b of the address space 23 in which a program 25 is stored based on the symbol 24, a control means 14 which executes the program 25 by sending the leading address 23a and the final address 23b to an object 2 to be measured. a measuring means 15 which measures passing address space passing into the address space 23 and calculates the ratio of it by executing the program 25, and an output means 16 which outputs a calculated ratio, the symbol 24, and passing unfinished address space, etc.