An electronic apparatus comprising a high-frequency signal transmission line (10, 10a - 10q) and a metal article that are disposed in a casing, the high frequency signal transmission line (10, 10a - 10q) comprising: an element assembly that is obtained by laminating insulating layers (18a - 18d) and has a first main surface and a second main surface, wherein the element assembly has flexibility; a linear signal line disposed in the element assembly; a first ground conductor that is disposed on a side of the first main surface of the element assembly with respect to the signal line, faces the signal line via one of the insulating layers (18a - 18d), and continuously extends along the signal line, wherein a portion of the first ground conductor facing the signal line substantially no opening is disposed; and a second ground conductor that is disposed on a side of the second main surface of the element assembly with respect to the signal line, faces the first ground conductor via the signal line sandwiched therebetween, and has a plurality of openings arranged along the signal line, wherein the linear signal line, the first ground conductor and the second ground conductor form a stripline of a triplate structure, wherein a main surface of the high-frequency signal transmission line (10, 10a - 10q) near the first ground conductor with respect to the signal line is in contact with the metal article; wherein a main surface of the high-frequency signal transmission line (10, 10a - 10q) near the second ground conductor with respect to the signal line is opposed to the casing at a specified distance; wherein a distance between the linear signal line and the first ground conductor is greater than a distance between the linear signal line and the second ground conductor; wherein the element assembly includes a connection portion (12b, 12c) to be used for external connection and a line portion where the first ground conductor extends along the signal line; and wherein, in the line portion, the first ground conductor is electrically connected to the metal article. an element assembly that is obtained by laminating insulating layers (18a - 18d) and has a first main surface and a second main surface, wherein the element assembly has flexibility; a linear signal line disposed in the element assembly; a first ground conductor that is disposed on a side of the first main surface of the element assembly with respect to the signal line, faces the signal line via one of the insulating layers (18a - 18d), and continuously extends along the signal line, wherein a portion of the first ground conductor facing the signal line substantially no opening is disposed; and a second ground conductor that is disposed on a side of the second main surface of the element assembly with respect to the signal line, faces the first ground conductor via the signal line sandwiched therebetween, and has a plurality of openings arranged along the signal line, wherein the linear signal line, the first ground conductor and the second ground conductor form a stripline of a triplate structure, wherein a main surface of the high-frequency signal transmission line (10, 10a - 10q) near the first ground conductor with respect to the signal line is in contact with the metal article; wherein a main surface of the high-frequency signal transmission line (10, 10a - 10q) near the second ground conductor with respect to the signal line is opposed to the casing at a specified distance; wherein a distance between the linear signal line and the first ground conductor is greater than a distance between the linear signal line and the second ground conductor; wherein the element assembly includes a connection portion (12b, 12c) to be used for external connection and a line portion where the first ground conductor extends along the signal line; and wherein, in the line portion, the first ground conductor is electrically connected to the metal article.