To provide a window glass installing device of vehicle by which the installing work of a window glass can be carried out by a single worker.

A suction pad 9 which is moved synchronously with a cab 1, installed vertically rotatable along an auxiliary arm 8, to a main arm 7 rotatable 90° horizontally connected with a negative pressure generator 11 to the auxiliary arm 8, and sucked to a back panel 17; and a pushing pad 10 which is moved forward and rearward by a cylinder 14, and pushes by contacting to the outer surface of a window glass 3 set to the opening 2 of a rear window; are provided, and a change-over valve 13 to control to feed and exhaust a hydraulic pressure to the cylinder 14 by using the negative pressure of the suction pad 9 as the input signal is also provided.