Provided is a fraudulent message detection device that detects a fraudulent message transmitted to a bus in a bus network. The fraudulent message detection device includes: a resynchronization detector (124) that detects an edge of a signal on the bus and determines whether to perform resynchronization based on the edge, so as to adjust a sampling point that is a point in time when a voltage of the bus is read to obtain a logical value of the signal during a one-bit period; a transmission and receiving control unit (122) that obtains a first logical value and a second logical value during a one-bit period after the resynchronization detector (124) determines to perform the resynchronization, the first logical value being a logical value on the bus at a sampling point used before the edge is detected, the second logical value being a logical value on the bus at a sampling point after the resynchronization based on the edge is performed; a comparator (627) that compares the first logical value and the second logical value; and a fraud detection processing unit (628) that executes post-fraud-detection processing associated with a case in which a fraudulent message is detected, when the first logical value and the second logical value do not coincide.
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