An antenna device (1) includes a plurality of triplate lines (31, 32) each of which includes a central conductor (401/122A) arranged between one pair of outer conductors (30, 50/121A, 123A) parallel to each other, and a plurality of antenna elements (14a) to transmit high frequency signals distributed by the plurality of triplate lines (31, 32). The plurality of triplate lines (31, 32) include a first triplate line (31) and a second triplate line (32) arranged non-parallel to each other and at a predetermined angle therebetween so that respective central conductors (401/122A) of the first triplate line (31) and the second triplate line (32) are intersected and connected together.