A cutting tool holding device, comprising: a base, comprising: a mounting hole; and a through hole formed at a side of the mounting hole and communicated with the mounting hole; a positioning tube, comprising: an axial receiving hole formed within the positioning tube for receiving a cutting tool; an accommodated portion disposed at an end of the positioning tube for being installed into the mounting hole; and a limiting groove formed on a side of the accommodated portion; and a positioning member positioned in the through hole of the base, wherein the positioning member abuts against the limiting groove of the positioning tube, characterized in that the positioning member having a cross-sectional area changing gradually along an extending direction thereof is configured for pressing the positioning tube, and the through hole of the base is substantially circular, wherein a screw member is disposed in one end of the through hole, and the screw member has a head and a threaded body; wherein a ridge portion is disposed in the limiting groove of the positioning tube, and the ridge portion has a first surface; wherein the positioning member is substantially formed in a tube shape corresponding to the through hole and is inserted into the through hole from the other end of the through hole, wherein a positioning groove having an inclined plane is disposed on an outside of the positioning member, wherein the positioning groove corresponds to the ridge portion, wherein the inclined plane corresponds to and abuts against the first surface of the ridge portion, wherein a tightening thread is disposed on an inner surface of the positioning member for engaging with the threaded body of the screw member, whereby the positioning member is driven by the screw member for changing a pressing degree between the inclined plane and the positioning tube. a base, comprising: a mounting hole; and a through hole formed at a side of the mounting hole and communicated with the mounting hole; a mounting hole; and a through hole formed at a side of the mounting hole and communicated with the mounting hole; a positioning tube, comprising: an axial receiving hole formed within the positioning tube for receiving a cutting tool; an accommodated portion disposed at an end of the positioning tube for being installed into the mounting hole; and a limiting groove formed on a side of the accommodated portion; and an axial receiving hole formed within the positioning tube for receiving a cutting tool; an accommodated portion disposed at an end of the positioning tube for being installed into the mounting hole; and a limiting groove formed on a side of the accommodated portion; and a positioning member positioned in the through hole of the base, wherein the positioning member abuts against the limiting groove of the positioning tube, characterized in that the positioning member having a cross-sectional area changing gradually along an extending direction thereof is configured for pressing the positioning tube, and the through hole of the base is substantially circular, wherein a screw member is disposed in one end of the through hole, and the screw member has a head and a threaded body; wherein a ridge portion is disposed in the limiting groove of the positioning tube, and the ridge portion has a first surface; wherein the positioning member is substantially formed in a tube shape corresponding to the through hole and is inserted into the through hole from the other end of the through hole, wherein a positioning groove having an inclined plane is disposed on an outside of the positioning member, wherein the positioning groove corresponds to the ridge portion, wherein the inclined plane corresponds to and abuts against the first surface of the ridge portion, wherein a tightening thread is disposed on an inner surface of the positioning member for engaging with the threaded body of the screw member, whereby the positioning member is driven by the screw member for changing a pressing degree between the inclined plane and the positioning tube.