To overcome problems such that the great weight of a quick coupler at the mounting of the quick coupler exerts a bad influence upon the performance of a hydraulic backhoe and such that the manufacturing cost of a quick coupler device gets high to make application limited, in the conventional hydraulic excavator.

A link rod 1 equipped with a quick coupler function is composed of a link rod body 2 and a coupling fitting 3; a hydraulic-cylinder's-side boss 7 and a bucket's-side boss 8 are provided at both ends of the rod body 2; the boss 8 is composed of an integral-type boss having a C-shaped cross section; and a hook 13, which is pivotally mounted on an intermediate part of the boss having the C-shaped cross section, is supported oscillatably by the small-diameter hydraulic cylinder 11 which is pivotally mounted on the rod body 2. The boss 8 is made to abut on a pin 15 in a state in which the cylinder 11 is contracted; the cylinder 11 is extended; and the hook 13 is turned around a pin 12, so that the pin 15 can be prevented from coming off even during the operation of a bucket.