Vehicle attached component, and on-board antenna

The purpose of the present invention is to enable a secure attachment of an antenna element and to facilitate adjustment of the antenna element characteristics. Rearward of a spoiler (10) are formed a plurality of lateral grooves (22) extending in a left-right direction of a vehicle, and a plurality of vertical grooves (24) extending in a front-rear direction of the vehicle. The plurality of lateral grooves (22) and the plurality of vertical grooves (24) form latticed grooves (26) as grooves in the shape of a lattice for installing an antenna element (16). The antenna element (16) is formed by a conductive wire. One end of the antenna element (16) is connected to an amplifier (18), and the other end is opened. The antenna element (16) extends from the amplifier (18) via a power feeding groove (28) and the right-end one of the vertical grooves (24) to the rear end of the groove, from which the antenna element is fitted in a route along the most rearward one of the lateral grooves (22) to the vicinity of the left-end one of the vertical grooves (24), thus being securely attached to the spoiler (10).