The properties of brittle materials such as ceramics are closely related to microcracks and their propagation in the microstructure. In this study, we constructed a simulation model to evaluate microcrack propagation in brittle polycrystalline materials. We used the phasefield crack model to represent crack propagation and the multi-phase-field model to represent the polycrystalline structure. To evaluate the basic characteristics of this model, we examined the driving force term and the threshold value of elastic strain energy for crack propagation. The validity of this model was confirmed by comparing the driving force term with that of another model having a different energy density function. The threshold value was determined by comparing the simulation and theoretical values of the start time of crack propagation. Furthermore, we evaluated the crack propagation path in a bicrystal and a polycrystal. a computational domain for a declined straight grain boundary. As a result, the transgranular and intergranular crack propagation could be reproduced depending on the amount of grain boundary inclination.