The invention discloses a device for synchronously measuring axial displacement and radial displacement of a rigid coupler. The device comprises a supporting rod which is connected in opposite connecting holes of two half couplers in a penetrating mode, a support is fixedly installed on the supporting rod, an axial measuring device measuring the axial displacement of the coupler and a radial measuring device measuring the radial displacement of the coupler are arranged on the support, threads are arranged on the supporting rod, the supporting rod and the coupler are connected through a pair of nuts I which are arranged on the supporting rod and positioned on the two sides of the coupler, and the support is installed on the supporting rod in a sleeved mode and fixed through a pair of nuts II. The device is simple in structure and convenient to operate, by the adoption of the axial measuring device and the radial measuring device which are installed on the support, axial displacement deviations and radial displacement deviations of the rigid coupler can be measured simultaneously, accumulative errors caused by separated measuring are reduced to the maximum, and measurement accuracy is improved substantially.