Antenna device and antenna module

An antenna module comprising:

• an antenna device includes:
• a substrate,
• a ground layer provided on a first surface of the substrate or in an inner layer of the substrate,
• a plurality of antenna elements arranged on a second surface of the substrate in an array,
• a plurality of dummy antenna elements arranged around the plurality of antenna elements in a plan view;
• and
• a phase controller configured to control a phase of a radio wave transmitted or received via the plurality of antenna elements, wherein
• the plurality of antenna elements includes an antenna element, the antenna element is configured to construct a patch antennae,
• the plurality of dummy antenna elements includes a dummy antenna, the dummy antenna is coupled to the ground layer by a conductive through portion, the conductive through portion passing through the substrate in a thickness direction and having conductivity, and
• a position of the conductive through portion with respect to the dummy antenna element in a plan view is a first position on a straight line that evenly divides an angle between a first straight line and a second straight line, or a second position in the neighborhood of the first position, the first straight passing through a first feed point and a center of dummy antenna element, the second straight passing through a second feed point and the center of dummy antenna element, the first feed point and the second feed point being feed points when the dummy antenna element generates circularly polarized waves.