It is an object of the present invention to provide an improved technique for preventing leakage of lubricant from an accommodating space that houses a driving mechanism, while regulating the internal pressure of the accommodating space in a power tool. A representative power tool includes a power tool body, a tool bit, a driving mechanism, a lubricant, an accommodating space, a passage and a lubricant leakage preventing region. The accommodating space is disposed in the body to house the driving mechanism and is hermetically sealed. The passage has an accommodating space side opening and an outside opening. The passage extends, starting from the accommodating space side opening, in a direction away from the outside opening. Then, the passage turns around and extends toward the outside opening. Further, the lubricant leakage preventing region is provided with the passage to prevent the lubricant from leaking from the inside to the outside of the accommodating space. According to the invention, the length of the passage can be made longer and the lubricant must travel a longer distance before leaking out. Therefore, a higher effect of preventing leakage can be obtained.