To provide a soundproof device reducing noise generated in a work construction by using a crushing tool such as a concrete breaker, more particularly, noise due to discharge of pressurized and discharged air from an exhaust hole in the crushing tool driven by air, and imparting no hindrance when laying the crushing tool.

A main body 2a of the crushing tool is covered in a sealed state from the exhaust hole 7 to a region at an upper end part with a soundproof cover 8 attachably/detachably mounted on the main body 2a, and an annular space is left in the space to form a pressurized and discharged air flow passage 12. The soundproof cover 8 is separated into a cap part 8a and a body part 8b. In the cap part 8a, a silencer 13 is incorporated. The pressurized and discharged air discharged from the exhaust hole 7 rises through the annular pressurized and discharged air flow passage 12 and is discharged to the outside through the silencer 13, and thereby exhaust sound of air and noise from an air driving part are considerably reduced.