An antenna device, comprising: a first conductor layer; a second conductor layer that is located opposite to the first conductor layer; a first dielectric layer that is located between the first conductor layer and the second conductor layer; a third conductor layer that is located opposite to the second conductor layer; and a second dielectric layer that is located between the second conductor layer and the third conductor layer, wherein the first conductor layer includes: a feed element to which power is supplied; a first grounding element that is located next to the feed element in a first direction via a first gap and grounded; and a parasitic element that is located along the feed element and the first grounding element and insulated from the feed element and the first grounding element, the second conductor layer includes: a floating element that is located opposite to the feed element and the parasitic element and insulated from the first conductor layer; a second grounding element that is located opposite to the first grounding element and the parasitic element and next to the floating element in the first direction via a second gap, and grounded; the third conductor layer includes a third grounding element that is located opposite to the floating element and the second grounding element and grounded; wherein the second conductor layer further includes: a first intermediate element (33, 33A, 33D) that is located, in the second gap, opposite to the parasitic element and extends in a second direction that intersects the first direction; a second intermediate element (34, 34A, 34D) that is located, in the second gap, next to the first intermediate element (33, 33A, 33D) in the second direction via a third gap and extends in the second direction, and the third gap at least partially overlaps at least one of the feed element, the first grounding element, and the first gap in a plan view of the first conductor layer. a first conductor layer; a second conductor layer that is located opposite to the first conductor layer; a first dielectric layer that is located between the first conductor layer and the second conductor layer; a third conductor layer that is located opposite to the second conductor layer; and a second dielectric layer that is located between the second conductor layer and the third conductor layer, wherein the first conductor layer includes: a feed element to which power is supplied; a first grounding element that is located next to the feed element in a first direction via a first gap and grounded; and a parasitic element that is located along the feed element and the first grounding element and insulated from the feed element and the first grounding element, a feed element to which power is supplied; a first grounding element that is located next to the feed element in a first direction via a first gap and grounded; and a parasitic element that is located along the feed element and the first grounding element and insulated from the feed element and the first grounding element, the second conductor layer includes: a floating element that is located opposite to the feed element and the parasitic element and insulated from the first conductor layer; a second grounding element that is located opposite to the first grounding element and the parasitic element and next to the floating element in the first direction via a second gap, and grounded; the third conductor layer includes a third grounding element that is located opposite to the floating element and the second grounding element and grounded; a floating element that is located opposite to the feed element and the parasitic element and insulated from the first conductor layer; a second grounding element that is located opposite to the first grounding element and the parasitic element and next to the floating element in the first direction via a second gap, and grounded; the third conductor layer includes a third grounding element that is located opposite to the floating element and the second grounding element and grounded; wherein the second conductor layer further includes: a first intermediate element (33, 33A, 33D) that is located, in the second gap, opposite to the parasitic element and extends in a second direction that intersects the first direction; a second intermediate element (34, 34A, 34D) that is located, in the second gap, next to the first intermediate element (33, 33A, 33D) in the second direction via a third gap and extends in the second direction, and the third gap at least partially overlaps at least one of the feed element, the first grounding element, and the first gap in a plan view of the first conductor layer. a first intermediate element (33, 33A, 33D) that is located, in the second gap, opposite to the parasitic element and extends in a second direction that intersects the first direction; a second intermediate element (34, 34A, 34D) that is located, in the second gap, next to the first intermediate element (33, 33A, 33D) in the second direction via a third gap and extends in the second direction, and the third gap at least partially overlaps at least one of the feed element, the first grounding element, and the first gap in a plan view of the first conductor layer.