Fault slip is initiated by locally applied fluid pressure, and it can expand unstably over a wide area causing elastic waves having magnitudes that induce felt or destructive earthquakes. Thus, it is important to examine the unstable expansion of initial slips. However, it is hard to reproduce the process by general setup of laboratory experiment such as triaxial loading tests on cylindrical specimens with inclined faults. In this study, we prepared a cubic specimen of sub-meter scale, which was separated into two triangular prisms by a model fault. The specimen was subjected to bi-axial compressions with different magnitudes. A 2D array of strain gauges was embedded beneath the fault plane to measure the changes in shear strain with the fault slip driven by fluid injection. Based on the experimental results, we discussed the features of fault slips that lead to injection-induced earthquake. The dataset obtained by the experiments were presented in the current data repository.