PURPOSE: To move the pump center without changing the pump posture in the case of adjusting tension of a belt by providing a bendable link between a pump and a first bracket and forming an arcuate groove of a shape similar to an arcuate locus described by one end on the pump side of the link in a second bracket.

CONSTITUTION: Two brackets 20, 21 are secured onto a side wall of an engine 31 with a bolts. One end of a link 24 is secured to a first bracket 20 with a bolt 28 either bendably or fixedly and a pump is secured to the other end of the link 24 with a bolt 27 either bendably or fixedly. An arcuate groove 32 of a shape similar to an arcuate locus described by one end on the pump side of the link 24 is formed in a second bracket 21. One end of a pump bracket 25 is secured to the arcuate groove 32 in a fixable manner via movable engaging bolt 26. A pulley 23 can thus be moved along with the move of a pump center 29 without changing posture of a pump 33 in the case of adjusting tension of a belt 32.