This disclosure provides a slot array antenna, which includes an emission waveguide having a conductor surface where emission slot rows are formed and for guiding electromagnetic waves to be emitted from the emission slot rows, each of the emission slot rows having a plurality of emission slots are arrayed in line, and a lattice. The lattice includes a plurality of conductor walls formed in a planer shape so as to extend in a direction intersecting with the conductor surface and repeatedly arranged corresponding to the plurality of emission slots, and a base plate coupling and fixing the plurality of conductor walls thereto, the base plate being fastened to the conductor surface of the emission waveguide.