Achieve an extinction ratio in the approximate 10−6 class for intensity transmittance in the terahertz band with one element. A wire grid device configured from layering a plurality of film substrates each formed from a rectangular polymer film wherein a narrow rectangular metal thin plate is formed in the approximate center of one face thereof. By having the width of the metal thin plate be approximately 1.0 mm, the length of the metal thin plate be approximately 12.0-30 mm, and the thickness of the film substrate be approximately 0.5-50 μm, it is possible to easily achieve an extinction ratio in the approximate 10−6 class for intensity transmittance in the terahertz band with one element.