A package structure of a power module is provided. The package structure includes a body having a sidewall, a first protruding structure protruding outward from one end of the sidewall, a second protruding structure protruding outward from another end of the sidewall and opposite to the first protruding structure, and a spring having two ends embedded in the first and the second protruding structures, respectively. The stress is transferred to the first and the second protruding structures via the spring, respectively. The equivalent stiffness of the spring is different from that of the body so that the package structure as a whole suffers the stress uniformly.