A slot array antenna that includes radiation, base, and grating plates is disclosed. The radiation plate has a first surface having multiple slots to radiate radio waves, second and third surfaces forming a horn shape, and proximal and distal connecting members. The base plate has first, second, and third surfaces forming a U-shape, and notches. The connecting members of the radiation are removably insertable into the notches to assemble the slot array antenna for the radiation of the radio waves and to suppress noise signals.