To prevent defective connection and rotation of a coupler for freely detachably connecting the side of a working machine to the side of an electric cable on the side of a machine body following the installation and removal of the working machine from the machine body.

This apparatus for coupling a working machine to a tractor is obtained by covering at least the upper part on the side of a base end of a coupler 44 with a bracket 57 capable of movably and elastically supporting either one of the couplers 44 and 46 capable of freely detachably connecting an electric cable 42 on the side of a working machine to an electric cable 43 on the side of a machine body following the installation and removal of the working machine from the machine body with an autohitch 3 capable of coupling and mounting the working machine on the machine body of the tractor by operations on the side of a driver's seat and forming the bracket 57 into a box shape provided with an opening 57d in the lower part thereof.