A method for manufacturing a liquid-crystal antenna device is provided. The method includes step (a) providing a first mother substrate. The first mother substrate includes a first region and a second region. The first region has a plurality of first sides. An extension line of at least one of the first sides divides the second region into a first part and a second part. The method also includes the following steps: (b) forming a first electrode layer on the first region and the second region, and (c) cutting the first mother substrate along the first sides of the first region.