PURPOSE: To change the dimension of a viscous matter jetted out of a jet nozzle for the viscous matter without damaging the shape of the viscous matter.

CONSTITUTION: A second constituent piece 220 and a third constituent piece 230 having different contact faces with a first constituent piece 210 can be slid in the direction of crossing each other without forming a clearance from the first constituent piece 210, while the surface 241 of a fourth constituent piece 240 facing the first constituent piece 210 is brought into contact with the side face 222 of the second constituent piece 220 and can be slid along the surface of the third constituent piece 230. Any proper constituent piece out of the above constituent pieces, therefore, can be slid properly for the first constituent piece 210 by operating a first supporting tool 310 and a second supporting tool 320 in the respective sliding direction to which the height and width of clearances encircled by respective constituent pieces can be changed, and at that time the changes can be carried out without forming the clearances among respective constituent pieces. Auxiliary wall plates used heretofore for eliminating the clearances formed on the inner wall of a nozzle, therefore, are not required.