PURPOSE: To simply carry out the regulation of the tensile force of a V-blet by joining a motor base to a motor with a special screw and providing a tension bolt with the functions of fixing the motor and regulating the tensile force of the V-belt.

CONSTITUTION: A motor 1 is fixed by means of a motor bolt 6 and a special motor bolt 10. A left-hand thread is formed on the right hand of a tension bolt 12 while forming a right-hand thread on the left hand thereof. With the tension bolt 12 and the special motor bolt 10 in a body by rotating an adjusting nut 13, the motor 1 is moved leftward to increase the tensile force of a V-belt 3. Thereby, the regulation of the tensile force of the V-blet can be simply carried out.