Transmission line and electronic device

A transmission line comprising:

• a multilayer body with a structure in which a plurality of insulator layers are laminated in an up-down direction where an up direction is a first direction and a down direction is a second direction;
• a signal conductor layer in the multilayer body and extending in a front-back direction orthogonal to the up-down direction;
• and
• a first ground conductor layer in the multilayer body above the signal conductor layer in the first direction and extending in the front-back direction to overlap the signal conductor layer when viewed in the up-down direction;
• wherein
• the multilayer body includes a first hollow portion;
• the first hollow portion is above the signal conductor layer in the first direction and below the first ground conductor layer in the second direction;
• the first hollow portion overlaps the first ground conductor layer when viewed in the up-down direction;
• the multilayer body includes a first spacer that faces the first hollow portion;
• in a cross section orthogonal to the front-back direction, a first overlapping region is a region in the first hollow portion in which the first hollow portion overlaps the first spacer in the up-down direction;
• in a cross section orthogonal to the front-back direction, a first non-overlapping region is a region in the first hollow portion in which the first hollow portion does not overlap the first spacer in the up-down direction;
• and
• a length of the first hollow portion in the up-down direction in the first overlapping region is shorter than a length of the first hollow portion in the up-down direction in the first non-overlapping region.