To provide an attachment for a tool with a compass capable of using a rotary power tool such as a rotary drill to be used for a boring tool such as a drill bit as a power tool for cutting a material to be cut.

A compass 40 for guiding this attachment 11 for a tool in the circumferential direction is provided in this attachment 11 for a tool comprising an input section 16 detachably attached to a rotating part 14a of the rotary power tool 14, an installation section 17 wherein a cutting tool 13 for cutting the material 15 to be cut with reciprocation thereof is attached, and a power converting section for converting rotation of the input section 16 to reciprocation so as to reciprocate the installation section 17.