COMPLEX MARKING DETERMINING DEVICE AND COMPLEX MARKING DETERMINING METHOD

A complex marking determining device (1; 1a) includes an imaging portion (2) that captures an image of a traveling road of a vehicle, and obtains a traveling road image (60); a region setting portion (12) configured to set a lane marking display region (R1) in a position where a lane marking is displayed, in the traveling road image obtained by the imaging portion, and set a road surface display region (R2) in a position that is closer to the center of the traveling road than the lane marking display region, and where a road surface other than the lane marking is displayed, in the traveling road image; a brightness state calculating portion (13) configured to calculate a lane marking representative value indicative of a brightness state of a plurality of pixels that make up the lane marking display region, and calculate a road surface representative value indicative of a brightness state of a plurality of pixels that make up the road surface display region; and a complex marking determining portion (14) configured to determine that the lane marking is a complex marking at least when a degree of deviation between the lane marking representative value and the road surface representative value is equal to or greater than a first threshold value.