A flat cable includes a base material including a signal conductor extending in a first direction, a first ground conductor, and a second ground conductor. The second ground conductor includes elongated conductors extending in the first direction, and bridge conductors that connect the elongated conductors at predetermined spacings along the first direction. The second ground conductor is connected with via-hole conductors at predetermined positions in two mutually opposite directions along the first direction with respect to each of the bridge conductors. Countercurrents generated from a plurality of countercurrent generation points do not flow to the first ground conductor via a common via-hole but flow to the first ground conductor individually via separate via-hole conductors.