To provide an incorrect path monitor system for monitoring incorrect path information for the purpose of fraud or the like that may be included in path information received from an external autonomous system (AS) and incorrect path information caused by setting error or the like.

The incorrect path monitor system 101 includes: a BGP path information receiving means for receiving BGP path information received from the external AS; a BGP path information decision means configured on the basis of an IRR database and collating path information of a path information database including information items of Prefix, PrefixLength, and an Origin AS number with Prefix, PrefixLength, and an Origin AS number of the BGP path information received from the external AS to decide the BGP path information received from the external AS; and BGP path information transmission means for transmitting the BGP path information decided by the BGP path information decision means to an edge router.