The present invention is configured such that a control device for a lane departure warning device that outputs a warning on the basis of the position relationship of a vehicle and a lane boundary line is equipped with a detection unit for detecting a switch of a brake from on to off, and a warning control unit for, when the detection unit has detected said switch, changing a warning threshold value to which vehicle position information is compared in the determination of whether or not to issue a warning to a value at which a warning is less likely to be issued as compared to when the detection unit has not detected said switch. The present invention thereby provides a control device for a lane departure warning device that is capable of reducing warnings which could be an annoyance to drivers.