To facilitate maintenance and insepection work in a truss without detaching a staircase by displaying an image showing the status in the truss photographed by a television camera provided in the truss of a man conveyer on a monitor television, and recording the image on a recording medium in such a manner as to be reproduced on the monitor television.

Devies installed in a truss are image-picked up by television cameras 1a, 1b installed in the upper part of the interior of the truss of an escalator. At this time, images photographed by the right television camera 1a or the left television camera 1b are stored to be used as hysteresis data in a recording medium of a storage device 12 for projecting the images on a monitor television 11 installed in a monitor room or a control building manager office, and reproduced by the monitor television 11 or a display 13 at need. Thus, it is possible to simply and surely confirm the status of the devices in the truss, for example the rotation status of front wheels and rear wheels of the step and the rotation status of the rubber handrail driving mechanism without detaching the staircase.