The present invention provides a vehicle body-embedded antenna device that can be embedded in a portion depressed in a metal body of a vehicle.　This vehicle body-embedded antenna device comprises a planar antenna element 10, a circuit substrate 20, and a fixed conducting part 30. The planar antenna element 10 is disposed substantially parallel to the metal body surface at the highest possible level where the planar antenna element can be disposed in the interior of a bathtub-shaped part 1. The circuit substrate 20 is disposed in the interior of the bathtub-shaped part 1 so as not to overlap the planar antenna element 10 in a top view, and has a power feeding part 21 to which the planar antenna element 10 is connected. The fixed conducting part 30 is electrically conductive to the circuit substrate 20 and also electrically conductive to the bathtub-shaped part 1, and is fixed to the bottom of the bathtub-shaped part 1 via a mounting hole 2 at the bottom of the bathtub-shaped part 1.