Provided is a simply fabricable small zeroth-order resonant antenna with extended bandwidth and high efficiency. The zeroth-order resonant antenna includes a feeding patch, a transmission line, and a pair of ground patches. The feeding patch is disposed on a top surface of a substrate having a mono-layer structure, and is configured to receive a signal from the outside. The transmission line includes a unit cell disposed on the top surface of the substrate and is configured to transmit a signal delivered from the feeding patch. The pair of ground patches is longitudinally disposed on the top surface of the substrate in the same direction as a longitudinal direction of the transmission line around the transmission line. The unit cell includes an upper patch and an inductor unit. The upper patch is disposed on the top surface of the substrate and is configured to receive a signal.