An antenna includes a housing of a resin, a first conductor group, and a power supply line. The housing includes first and second surfaces opposite in a first direction, third and fourth surfaces opposite in a second direction, and a housing portion surrounded by the first-fourth surfaces. The third surface connects the first and second surfaces. The first conductor group includes a first conductor, a second conductor, a second conductor group, and a third conductor. The first conductor is closer to the first surface than the second surface. The second conductor is closer to the second surface than the first surface. The second conductor group extends along the third surface and capacitively couples the first and second conductors. The third conductor extends along the fourth surface and electrically connects the first and second conductors. The power supply line is connected to any one portion of the second conductor group.