We propose a wideband and dual polarization open-ended waveguide. Because excitation probes of the waveguide and strip lines connected to the probes are formed in the dielectric substrate, multiple elements can be fed by using the branched strip line. So the proposal makes it easy to construct array antennas. In order to array the antennas including the strip lines with suitable spacing, we propose to miniaturize cavity size of the waveguide and to attach parasitic elements for impedance matching. We designed the antenna element. Low reflection levels for both polarizations are obtained.