A millimeter wave antenna and a process design of a millimeter wave antenna are provided. The millimeter wave antenna includes a substrate and an antenna attached to the substrate. The substrate includes a first region and a second region. A thickness of the first region is less than a thickness of the second region. The antenna is arranged on the first region. According to the present application, the millimeter wave antenna enables the substrate attached with the antenna to be as thin as possible, such that a medium structure of the first region of the substrate is changed, reducing an energy loss while a millimeter wave is being transmitted.