An antenna device includes: a first sub-array antenna provided on a substrate and having a group of first antenna elements, one or more third antenna elements, and a first electrical power line through which electric power is supplied to the group of first antenna elements and the one or more third antenna elements; and a second sub-array antenna provided on the substrate and having a group of second antenna elements, the one or more third antenna elements, and a second electrical power line through which electric power is supplied to the group of second antenna elements and the one or more third antenna elements. The one or more third antenna elements are placed away from the first electrical power line and the second electrical power line.