A cutting tool comprising: a shaft extending along a rotation axis (A) and having a first end portion and a second end portion ; and a sensor device , wherein the cutting tool is configured to cut a workpiece by rotating around the rotation axis (A) of the shaft , wherein the sensor device includes a sensor module including a plurality of first sensors configured to detect a first physical quantity of the shaft and a substrate electrically connected to the first sensors, characterised in that the sensor device is disposed in such a manner as to surround a portion of the shaft in a longitudinal direction of the shaft , and the sensor module further includes a wireless communication unit electrically connected to the substrate and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and a housing accommodating the sensor module , wherein a region of the shaft surrounded by the sensor device includes a first region having a shape of a 4n-sided polygon when viewed from a direction in which the rotation axis (A) extends, wherein the n is a natural number of two or more, and wherein, when viewed from the direction in which the rotation axis (A) extends, the plurality of first sensors are arranged on at least two of outer peripheral surfaces of the first region, each of outer peripheral surfaces of the first region corresponding to one of sides of the 4n-sided polygon, perpendicular lines (L A , L B ) of the at least two outer peripheral surfaces passing through the rotation axis (A) and intersecting each other at 90 degrees. a shaft extending along a rotation axis (A) and having a first end portion and a second end portion ; and a sensor device , wherein the cutting tool is configured to cut a workpiece by rotating around the rotation axis (A) of the shaft , wherein the sensor device includes a sensor module including a plurality of first sensors configured to detect a first physical quantity of the shaft and a substrate electrically connected to the first sensors, characterised in that the sensor device is disposed in such a manner as to surround a portion of the shaft in a longitudinal direction of the shaft , and the sensor module further includes a wireless communication unit electrically connected to the substrate and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and a housing accommodating the sensor module , a sensor module including a plurality of first sensors configured to detect a first physical quantity of the shaft and a substrate electrically connected to the first sensors, characterised in that the sensor device is disposed in such a manner as to surround a portion of the shaft in a longitudinal direction of the shaft , and the sensor module further includes a wireless communication unit electrically connected to the substrate and configured to transmit a signal including information of the first physical quantity detected by the first sensors to outside and a housing accommodating the sensor module , wherein a region of the shaft surrounded by the sensor device includes a first region having a shape of a 4n-sided polygon when viewed from a direction in which the rotation axis (A) extends, wherein the n is a natural number of two or more, and wherein, when viewed from the direction in which the rotation axis (A) extends, the plurality of first sensors are arranged on at least two of outer peripheral surfaces of the first region, each of outer peripheral surfaces of the first region corresponding to one of sides of the 4n-sided polygon, perpendicular lines (L A , L B ) of the at least two outer peripheral surfaces passing through the rotation axis (A) and intersecting each other at 90 degrees. <EOS>