A multi-antenna communication device is provided, including a grounding conductor plane separating a first side space and a second side space and having a first edge. A four-antenna array including first, second, third and fourth antennas is located at the first edge, and has an overall maximum array length extending along the first edge. The first and second antennas are located in the first side space, and the third and fourth antennas are located in the second side space. Each of the first to fourth antennas includes a feeding conductor line, a grounding conductor line, and a radiating conductor portion electrically connected to a signal source through the feeding conductor line and electrically connected to the first edge through the grounding conductor line, thereby forming a loop path and generating at least one resonant mode. The radiating conductor portion has a corresponding projection line segment at the first edge.