This paper aims to introduce two types of submillimeter-wave horn antennae designed by the authors and to present numerical findings obtained by an evaluative testing system that has also been developed by the authors. Submillimeter-wave components are widely used in radio-astronomical observation systems. There is a need to minimize (1) the various losses possibly incurred in the wave-receiving unit, and (2) the quantity of the unwanted electromagnetic waves mixing in. It is a well-known fact that a corrugated horn antenna possesses very low levels of cross-polarized field intensity, loss, and side lobes. It is for this reason that the authors have chosen to use corrugated horn antennae as two types of such antennae — one designed for use in the range of 280GHz to 360GHz frequencies and tested at 280GHz, 332GHz, and 360GHz, and the other designed for use in the range of 385GHz to 500GHz frequencies and tested at 385GHz, 442.5GHz, and 500GHz. The measurements of the antenna beam patterns have been found to largely correspond to those of the numerical analyses; it may be concluded that the antennae are functionally as efficient as they were designed and the testing system doubtless serves the desired purpose.