The invention discloses a gear shifting performance offline detecting device of a manual transmission. The device comprises X-axle, Y-axle and Z-axle linear modules; a rotating joint is added between the Y-axle linear module and the Z-axle linear module; a centering and torque measuring mechanism is fixed on a slide table of the Z-axle linear module; the rotating joint includes a stepper motor, a speed reducer, an adapting block, a support and a cross roller bearing; and the centering and torque measuring mechanism includes a stepper motor, a speed reducing structure, a first bracket, a torque sensor, an adapting block, a second bracket, a three-way force sensor, a cross roller bearing, a mandrel and a two-jaw cylinder. As the rotating joint is added between the Y-axle linear module and the Z-axle linear module, the Z-axle linear module can rotate around the Y-axle linear module to adapt the attitude variation of gear shifting rocker arm heads of manual transmissions with different model numbers; and the device has the advantages of automatic centering of a manipulator and a rocker arm, compact structure, easy assembly, integrated control and low cost.