To provide a grill installation structure that is capable of firmly supporting an air outlet of a grill body of an air-conditioning grill to a grill installation part of an installation member even when the grill installation part of the installation member is designed to have a notched shape. A finisher of the grill installation part is formed in a notched shape such that an air-conditioning grill unit is insertable in a direction (grill insertion direction Ig) orthogonal to an opening direction of the air outlet, and the finisher includes a grill fixing part on the back. The air-conditioning grill unit includes an outer peripheral flange disposed frontward to a front surface side of the finisher, and the air-conditioning grill unit includes a grill holding plate that is installed in the grill fixing part from a back thereof.