A base station device (10) for carrying out radio communications with a mobile station device includes: a frequency channel assigning unit (12) for assigning multiple mutually different frequency channels to the mobile station device; a communication quality information acquiring unit (13) for acquiring communication quality information indicating communication quality for each o the multiple frequency channels assigned to the mobile station device by the frequency channel assigning unit; and an interference wave existence judging unit (14) for judging whether or not an interference wave exists for each of the multiple frequency channels assigned to the mobile station device by the frequency channel assigning unit (12), on the basis of a difference in the communication quality information between the frequency channels acquired by the communication quality information acquiring unit (13).