A roller burnishing tool device comprising: a shank to be attached to a processing machine; a housing connected to the shank, a connected position of the housing relative to the shank being adjustable in a front-rear direction; a roller support member having an annular shape in a cross section thereof, supported so as to be capable of rotating relative to the housing, and disposed so as to follow a movement of the housing in a case where the connected position of the housing relative to the shank is adjusted to be changed; rollers having tapered shapes and supported by the roller support member; a mandrel having a tapered portion matched with the tapered shapes of the rollers and inserted in the roller support member coaxially; and a tool diameter following mechanism connecting the shank and the mandrel, the tool diameter following mechanism including: a hollow cylindrical portion formed at a front portion of the shank, a lead groove formed spirally in the hollow cylindrical portion, the lead groove being configured to pass through the hollow cylindrical portion; a pin member disposed so as to be capable of moving spirally along the lead groove, the pin member having a cylindrical hollow pin, two bolts and two bearings, the two bolts being attached to respective end portions of the cylindrical hollow pin, the two bearings being positioned between an outer surface of the mandrel and the respective bolts and the two bearings being attached so that the respective end portions of the cylindrical hollow pin are inserted in the two bearings and so that respective outer rings of the two bearings can be guided along the lead groove; a pin member insertion hole formed in the mandrel, which hole the cylindrical hollow pin of the pin member is inserted in, and a biasing unit attached to the shank and biasing the mandrel forward. a shank to be attached to a processing machine; a housing connected to the shank, a connected position of the housing relative to the shank being adjustable in a front-rear direction; a roller support member having an annular shape in a cross section thereof, supported so as to be capable of rotating relative to the housing, and disposed so as to follow a movement of the housing in a case where the connected position of the housing relative to the shank is adjusted to be changed; rollers having tapered shapes and supported by the roller support member; a mandrel having a tapered portion matched with the tapered shapes of the rollers and inserted in the roller support member coaxially; and a tool diameter following mechanism connecting the shank and the mandrel, the tool diameter following mechanism including: a hollow cylindrical portion formed at a front portion of the shank, a lead groove formed spirally in the hollow cylindrical portion, the lead groove being configured to pass through the hollow cylindrical portion; a pin member disposed so as to be capable of moving spirally along the lead groove, the pin member having a cylindrical hollow pin, two bolts and two bearings, the two bolts being attached to respective end portions of the cylindrical hollow pin, the two bearings being positioned between an outer surface of the mandrel and the respective bolts and the two bearings being attached so that the respective end portions of the cylindrical hollow pin are inserted in the two bearings and so that respective outer rings of the two bearings can be guided along the lead groove; a pin member insertion hole formed in the mandrel, which hole the cylindrical hollow pin of the pin member is inserted in, and a biasing unit attached to the shank and biasing the mandrel forward. a hollow cylindrical portion formed at a front portion of the shank, a lead groove formed spirally in the hollow cylindrical portion, the lead groove being configured to pass through the hollow cylindrical portion; a pin member disposed so as to be capable of moving spirally along the lead groove, the pin member having a cylindrical hollow pin, two bolts and two bearings, the two bolts being attached to respective end portions of the cylindrical hollow pin, the two bearings being positioned between an outer surface of the mandrel and the respective bolts and the two bearings being attached so that the respective end portions of the cylindrical hollow pin are inserted in the two bearings and so that respective outer rings of the two bearings can be guided along the lead groove; a pin member insertion hole formed in the mandrel, which hole the cylindrical hollow pin of the pin member is inserted in, and a biasing unit attached to the shank and biasing the mandrel forward.