The scanning antenna (1000) is a scanning antenna in which antenna units (U) are arranged, the scanning antenna including: a TFT substrate (101) including: a first dielectric substrate (1), TFTs, gate bus lines, source bus lines, and patch electrodes (15); a slot substrate (201) including: a second dielectric substrate (51), and a slot electrode (55); a liquid crystal layer (LC) provided between the TFT substrate and the slot substrate; and a reflective conductive plate (65). The slot electrode includes slots (57) arranged in correspondence with the plurality of patch electrodes, and a thickness of the second dielectric substrate (51) is smaller than the thickness of the first dielectric substrate (1) at least in a region where the antenna units (U) are arranged.