To improve operating efficiency by eliminating the interruption of operation by automatically changing over an image in response with operation of an operator.

In a monitor camera device for construction machinery having a rear monitor camera 12 monitoring the rear of the construction machinery and a front monitor camera 11 monitoring a front and selectively projecting the images by each monitor camera 11 and 12 onto one display 10, the monitor camera device has a pressure switch 59 detecting the execution of traveling operation and outputting a traveling detecting signal and a changeover circuit 60 changing over the image projected onto the display 10 from the image by the front monitor camera 11 to the image by the rear monitor camera 12 when the traveling detecting signal from the pressure switch 59 is at on.