The present application provides a switchable beam phase shifter and an antenna. The switchable beam phase shifter comprises an arc conductor assembly and a coupling assembly. The coupling assembly rotates about the center of the arc conductor assembly, and the arc conductor assembly comprises a first arc conductor and a second arc conductor. The first arc conductor and the second arc conductor are arranged in a circle around the center of the circle, one of the first arc conductor and the second arc conductor is a slow wave structure, and two ends of the first arc conductor and two ends of the second arc conductor are each provided with an output port. When the coupling assembly is located at a first position, the coupling assembly is coupled and electrically connected to the first arc conductor, and when the coupling assembly is located at a second position, the coupling assembly is coupled and electrically connected to the second arc conductor. The switchable beam phase shifter provided by the present application may switch between the two working states of a wide beam and a narrow beam by means of the coupling connection between the coupling assembly and different arc conductors, and has good impedance matching and relatively high practicality.