Deformation behaviour of semi-solid materials strongly influences defect formation in casting and semi-solid forming processes, and macroscopic deformation properties have been extensively evaluated using vane rheometers. From experimental observations, pronounced dependences on solid fraction and strain rate have been reported [1]. However, it has been pointed out that the widely used four-arm vane rheometer significantly disturbs the flow field due to its non-axisymmetric kinematics, making accurate evaluation of viscosity difficult [2]．Therefore, a numerical framework that enables systematic control of boundary conditions for applying external forces is required to evaluate the deformation behaviour of semi-solid materials. In our previous work, we developed a multi-phase-field lattice Boltzmann (MPF–LB) framework for simulating semi-solid simple shear deformation and clarified the mechanism of shear band formation from the perspective of grain rearrangement [3]. Building upon this foundation, in this study, we propose a phase-field-based numerical framework that represents vane rheometer experiments [1]. Semi-solid materials are generated using multi-phase-field simulations, and the shear loading is introduced through the prescribed motion of solid walls represented by phase-field variables. Furthermore, computation is performed with graphics processing units (GPUs). Through the simulations, the validity of the developed method is confirmed by comparing the simulation results with experiments. In addition, the results are compared with previously obtained simple shear simulation results, and relationships for evaluating viscosity from rheometer measurements based on the simulation results are explored.