VEHICULAR DOOR DEVICE

A vehicular door device includes a door-side engagement portion including a guide groove that includes a pair of side wall portions facing each other in a vehicle width direction and extends in an opening-closing operation direction of the door, a vehicle body-side engagement portion including a shaft-shaped engagement portion extending in an up-down direction of a vehicle, and an expansion mechanism provided in a second link arm. In an opening-closing operation position near a full closed position of the door where the door-side engagement portion and the vehicle body-side engagement portion engage with each other, the shaft-shaped engagement portion is disposed in the guide groove. The shaft-shaped engagement portion is relatively displaced along an extending direction of the guide groove while a change in length of the second link arm, based on an operation of the expansion mechanism, is accompanied, and thus the door can perform an opening-closing operation.