A high-frequency transmission line configured to stack a plurality of conductor layers (114, 116) and an insulating layer, the high-frequency transmission line comprising: a signal via that extends in a direction where the conductor (114, 116) and insulating layers are stacked and electrically connects the conductor layers (114, 116) to one another; an input line that is provided in one of the conductor layers (114, 116) to input an electric signal to the signal via; a signal line provided in another one of the conductor layers (114, 116) and connected to the input line through the signal via; a ground plane that is provided in at least one of one of the conductor layers (114, 116) in which the input line is provided, another one of the conductor layers (114, 116) in which the signal line is provided, and a further one of the conductor layers (114, 116) provided between the one conductor layer and the another one conductor layer, is spaced apart from the signal via, and is connected to a reference potential, GND; a conductor arm provided in a spacing region between the signal via and the ground plane; and a conductor connector that is provided in the spacing region to connect the conductor arm and the ground plane, wherein an outer edge of the signal via, a part of the spacing region, the conductor arm, and another part of the spacing region are arranged in this order in a direction from a center of the signal via to an outer edge of the spacing region, and the conductor arm and the conductor connector are configured to suppress a specific frequency electric signal of the electric signal, characterized in that the outer edge of the signal via, the part of the spacing region, the conductor arm, and the another part of the spacing region are arranged in this order in the direction from the center of the signal via to the outer edge of the spacing region at a level of a conductor layer of the ground plane where the conductor arm and the conductor connector are provided and a top view shape of the spacing region is substantially circular shape centered on the signal via. a signal via that extends in a direction where the conductor (114, 116) and insulating layers are stacked and electrically connects the conductor layers (114, 116) to one another; an input line that is provided in one of the conductor layers (114, 116) to input an electric signal to the signal via; a signal line provided in another one of the conductor layers (114, 116) and connected to the input line through the signal via; a ground plane that is provided in at least one of one of the conductor layers (114, 116) in which the input line is provided, another one of the conductor layers (114, 116) in which the signal line is provided, and a further one of the conductor layers (114, 116) provided between the one conductor layer and the another one conductor layer, is spaced apart from the signal via, and is connected to a reference potential, GND; a conductor arm provided in a spacing region between the signal via and the ground plane; and a conductor connector that is provided in the spacing region to connect the conductor arm and the ground plane, wherein an outer edge of the signal via, a part of the spacing region, the conductor arm, and another part of the spacing region are arranged in this order in a direction from a center of the signal via to an outer edge of the spacing region, and the conductor arm and the conductor connector are configured to suppress a specific frequency electric signal of the electric signal, characterized in that the outer edge of the signal via, the part of the spacing region, the conductor arm, and the another part of the spacing region are arranged in this order in the direction from the center of the signal via to the outer edge of the spacing region at a level of a conductor layer of the ground plane where the conductor arm and the conductor connector are provided and a top view shape of the spacing region is substantially circular shape centered on the signal via.