Abstract: The present invention relates to an extraction/insertion type soot blowing apparatus in which a lance tube is inserted into a combustion chamber, and a high-pressure gas is blown from a nozzle provided at the tip end of the lance tube against a deposit adhered onto the inner surface of the combustion chamber to remove the deposit. A rack adapted to be advanced and withdrawn along with the lance tube, and a long shaft for rotating the lance tube, are driven due to connection thereof with two output shafts of a differential gear device, and rotation and linear motion of the lance tube are respectively restrained within predetermined ranges. Thereby, at first the lance tube is inserted into the combustion chamber at a high speed without being rotated, and thereafter the advance is stopped and a gas is discharged while the lance tube is being rotated.