In this paper, we describe the fracture mechanisms of lead zirconate titanate (PZT) piezoelectric thin films synthesized by sol-gel processing. One of the technical concerns in piezoelectric thin films is how their surface fractures because, in most cases, the films fail electrically, and the fracture surface is remade after its first fracture. To estimate the failure mechanisms, cantilever-type and clamped capacitor-type actuators made of PZT piezoelectric thin films deposited on a Si wafer were prepared and subjected to electrical and mechanical stresses. The cantilever-type actuators showed a decreasing trend in dielectric withstand voltage with increasing number of mechanical loading cycles. The clamped capacitor-type actuators showed a decreasing trend in withstand voltage with increasing cyclic voltage amplitude. Through mechanical and electrical experiments, we found that the origin of cracking differed from that of short circuit. This finding indicates that the PZT films fractured mechanically, then fractured electrically. The focused ion beam fabrication of a surface defect and scanning electron microscopy observation around the defect suggest a reasonable fracture mechanism.