A millimeter wave band array antenna is disclosed. The disclosed antenna includes: a first dipole array antenna unit including first +dipole members, formed on an upper portion of a first substrate and provided with feed signals through a first feed line, and first −dipole members, formed on a lower portion of the first substrate and joined with a ground plane on a lower portion of the first substrate; and a slot antenna unit including slot radiators, which are formed on an upper portion of the first substrate, where the ground plane includes a first sloped structure having an upward slope of a first angle to the right from the point of junction with a first −dipole member and a second sloped structure having an upward slope of the first angle toward the left from the point of junction.