PURPOSE: To improve a field of vision and enhance workability and safety by providing display screens of less number than the number of video cameras for watching conditions of a front area, a rear area, and a load handling head of a vehicle, and a main switch circuit for selectively connecting a pair of the video cameras to the display screens.

CONSTITUTION: First and second switches are automatically set at positions MA, NA when a crane is set in a forward position 11A, and an image of a front area of a chassis 1 captured by video cameras A1, A2 is displayed on video monitor screens V1, V2 via a video link. When a reverse lever of the crane is changed to a backward position 11B, a circuit operates to display an image in a backward direction of the crane on the video monitor screens. At a neutral position 11C, the circuit operates to display an image captured by video cameras C1, C2 on the monitor screens V1, V2. Accordingly, safety and controllability of a work vehicle operated by a loading/unloading worker or the like can be significantly improved.