The invention discloses a cavity body phase shifter which comprises a cavity body formed integrally, a feed network arranged in the cavity body, dielectric elements arranged between the feed network and the cavity body, and at least one transmission line conversion device, wherein the transmission line conversion devices are welded and fixedly connected with the cavity body to be used for connection of the cavity body and external conductors of transmission cables, and to allow internal conductors of the transmission cables to penetrate into cavities of the cavity body to be connected with the feed network. The phase shifter makes rectilinear motion in a lengthwise direction of the cavity body by stress of the dielectric elements, so that a phase shifting purpose is achieved. The phase shifter is divided into the cavity body formed integrally and the transmission line conversion devices, so that design and processing difficulty requirements are reduced; and the phase shifter is connected without fixing pieces such as screws, so that hidden reliability and intermodulation dangers caused by screw failure are avoided.