Power tool

It is an object of the invention to provide a power tool that effectively prevents leakage of lubricant while regulating the internal pressure of a housing space for a driving mechanism. The object can be achieved by a representative power tool that includes a tool bit (119), a driving mechanism (113,115), an enclosed housing space (107a) which houses the driving mechanism and in which lubricant is sealed in, and a path (151) which regulates pressure of the housing space (107a). On the path, a filter chamber (154) having a predetermined capacity, an inner passage (155c) that communicates the filter chamber (154) with the housing space (107a), and an outer passage (159c) that communicates the filter chamber (154) with the outside are formed. A filter (157) is disposed in the filter chamber (154) and spaced apart from a peripheral edge of an opening of the outer passage (159c) which is open to the filter chamber (154), so that a space (161) is created on the opening edge side of the filter chamber (154). A throttle member (163,167) is disposed in the space (161) and throttles flow of air which flows out to the outer passage (159c) through the filter (157).