A planar array antenna 20 includes: a dielectric substrate; a conductive ground layer 37 formed on one surface of the dielectric substrate; a plurality of serial-type radiation element rows 41 formed on another surface of the dielectric substrate; and a parallel feed line that is formed on the other surface of the dielectric substrate and supplies high-frequency electric power between a feed end point 45s on the other surface of the dielectric substrate and the serial-type radiation element rows 41. The parallel feed line 45 branches from the feed end point 45s to the radiation elements 42 at ends of the serial-type radiation element rows closest to the feed end point 45s, and connects the feed end point 45s to the radiation elements 42, and all of the serial-type radiation element rows 41 an identical path length from the feed end point 45s to each of the radiation elements 42.