PURPOSE: To improve the carrying efficiency in making the size of a usable wheelchair confirmable by mixing a series of grooves in different directions, in an escalator installing a manhole cover formed with a lot of nonslipping grooves on the surface, on a vestibule floor free of detachment.

CONSTITUTION: A manhole cover 11 being installed on a vestibule floor of a wheelchair escalator 3 is provided with a lot of nonslipping grooves for passengers on the top surface. At the time of forming suchlike grooves, grooves 11a extending in the cross direction of steps 4 and other grooves 11b extending in the direction orthogonal with these grooves 11a are formed jointly, and a border line of these grooves 11a, 11b is made to act as a wheelchair size measuring gauge 12. When this escalator 3 is operated for a wheelchair, service personnel guides the wheelchair onto this measuring gauge 12 and, after checking the size of the wheelchair, its wheelchair operation is carried out. According to this method of installing this gauge 12 like this, it is made unobstrusive from people.