An antenna includes a dielectric substrate and an antenna element. The antenna element includes a power feeding element and a reference potential element. The power feeding element includes a first conductive layer formed over the dielectric substrate, the first conductive layer extending in a first direction and having a first length along the first direction. The reference potential element includes a second conductive layer formed over the dielectric substrate, the second conductive layer extending in a second direction opposed to the first direction from a second position, the second point being apart by a first distance from a first position on an end of the first conductive layer, and a third conductive layer formed over the dielectric substrate, the third conductive element extending from the second point in the first direction apart by a second distance from the first conductive layer and having a third length along the first direction.