Abstract: An access monitoring section (11) obtains access information including an address conforming to an address stored in a monitoring address setting section (10) from an access signal output from a CPU (1) to a peripheral device (3). An access judging section (13) compares the access information received from the access monitoring section (11) and the last access information stored in an access storing section (12), and stores the obtained access information in the access storing section (12) and requests the transmission of an exception generation notification to an exception generating section (14) when the received access information is different from the last access information while excluding the last access information stored in the access storing section (12) from access information to be compared when the received access information is the same as the last access information. By this construction, throughput can be reduced at the time of emulation and the peripheral device can be efficiently emulated.