Work machine perimeter monitoring device, and work machine perimeter monitoring method

The present invention includes: a perimeter monitor (15); a plurality of cameras for acquiring the surrounding state of a work machine; an image processing unit for generating an overhead image (61) on the basis of images taken by the plurality of cameras; a work machine operation detecting unit for detecting operation of the work machine; and a display control unit for displaying, on the perimeter monitor (15), a single camera image (62) that is an image from among one or more of the plurality of cameras, and/or the overhead image (61), and/or a machine gauge display, and/or a menu display, and/or a failure information display. If operation of the work machine is detected, the display control unit performs a control such that the display area of the overhead image (61) on the perimeter monitor (15) is larger than the display area of the overhead image (61) prior to detecting operation of the work machine. This can save the operator the trouble of operating the display screen.