A plate for an electro-thermal window comprising: a plate for a window; a transparent conductive film that can be heated; and a plurality of bus bars (13, 14) that feed power to the transparent conductive film; wherein the plurality of bus bars (13, 14) include a left bus bar connected to a left side edge part of the transparent conductive film and a right bus bar connected to a right side edge part of the transparent conductive film, wherein the transparent conductive film is divided into three or more regions (31A, 32A, 33A) by a plurality of slits (21A, 22A) that are continuously or discontinuously formed from the left bus bar to the right bus bar, wherein the plurality of regions (31A, 32A, 33A) include a first region and a second region, wherein a distance between the left bus bar and the right bus bar of the first region is shorter than a distance between the left bus bar and the right bus bar of the second region, and wherein a width of the first region in a direction orthogonal to the slit is shorter than a width of the second region in the direction orthogonal to the slit, wherein the transparent conductive film, by way of the plurality of slits (21A, 22A), forms a frequency selective surface through which a vertically polarized electromagnetic wave of a predetermined frequency band is transmitted, wherein a wavelength in the plate for an electro-thermal window satisfies λ g = λ 0 × k in a case where "λ 0 " is a wavelength of a center frequency in the predetermined frequency band in an atmosphere and "k" is a wavelength shortening rate of the plate for an electro-thermal window, wherein an interval at least between a pair of slits is less than or equal to λ g /4 and less than or equal to 43 mm. a plate for a window; a transparent conductive film that can be heated; and a plurality of bus bars (13, 14) that feed power to the transparent conductive film; wherein the plurality of bus bars (13, 14) include a left bus bar connected to a left side edge part of the transparent conductive film and a right bus bar connected to a right side edge part of the transparent conductive film, wherein the transparent conductive film is divided into three or more regions (31A, 32A, 33A) by a plurality of slits (21A, 22A) that are continuously or discontinuously formed from the left bus bar to the right bus bar, wherein the plurality of regions (31A, 32A, 33A) include a first region and a second region, wherein a distance between the left bus bar and the right bus bar of the first region is shorter than a distance between the left bus bar and the right bus bar of the second region, and wherein a width of the first region in a direction orthogonal to the slit is shorter than a width of the second region in the direction orthogonal to the slit, wherein the transparent conductive film, by way of the plurality of slits (21A, 22A), forms a frequency selective surface through which a vertically polarized electromagnetic wave of a predetermined frequency band is transmitted, wherein a wavelength in the plate for an electro-thermal window satisfies λ g = λ 0 × k in a case where "λ 0 " is a wavelength of a center frequency in the predetermined frequency band in an atmosphere and "k" is a wavelength shortening rate of the plate for an electro-thermal window, wherein an interval at least between a pair of slits is less than or equal to λ g /4 and less than or equal to 43 mm.