To provide a nailing machine having a silencer that is arbitrarily changeable in capacity in order to solve a problem that, when increasing a total height of the nailing machine by installing a large-capacity expansion chamber for reducing an exhaust sound, it becomes impossible to use a tool in a narrow place such as a space surrounded by columns.

The expansion chamber is expanded and a large sound reduction effect can be obtained by installing the expansion chamber of a cylindrical body structure at an exhaustion part of a body contour, and by making the cylindrical body extensible.