Provided is a fraudulent message detection device that detects a fraudulent message in a
bus network and includes: a resynchronization
detector that detects an edge of a
signal on a
bus in the
bus network and determines whether to perform resynchronization, so as to adjust a sampling point in a one-bit period; a transmission and receiving
control unit that obtains a first logical value and a second logical value in a one-bit period after the resynchronization
detector determines to perform the resynchronization, the first logical value being a logical value at a sampling point used before the edge is detected, the second logical value being a logical value at a sampling point after the resynchronization is performed; a
comparator that compares the first and second logical values; and a fraud detection
processing unit that executes post-fraud-detection
processing, when the first and second logical values do not coincide.