An implement attachment device , for selectively attaching an implement to a working machine, comprising - a hydraulic cylinder comprising a cylinder housing with first and second longitudinal ends, a piston in the cylinder housing, and a piston rod fixed to the piston and protruding through the first end of the cylinder housing, - an attachment element being connected to a protruding portion of the piston rod, and adapted to engage with a complementary element of the implement, and - a hydraulic conduit and valve arrangement (1201-1204), connected to the hydraulic cylinder , - characterized in that the conduit and valve arrangement (1201-1204) is arranged to selectively allow a communication between a piston side chamber of the hydraulic cylinder and a rod side chamber of the hydraulic cylinder , further characterized in that the conduit and valve arrangement (1201-1204) comprises - a control valve , - a conduit arrangement , arranged to provide a communication between the hydraulic cylinder and the control valve , and - a locking valve arranged to allow, in a first position, the communication between the hydraulic cylinder and the control valve by means of the conduit arrangement , and to allow, in a second position, the communication between the piston side chamber and the rod side chamber of the hydraulic cylinder by means of the conduit arrangement , wherein the conduit arrangement comprises a piston side conduit extending from the control valve to the piston side chamber of the hydraulic cylinder , and a rod side conduit extending from the control valve to the rod side chamber of the hydraulic cylinder . and wherein the locking valve is arranged to allow, in the first position, the communication between the hydraulic cylinder and the control valve through the piston side conduit as well as through the rod side conduit , and to allow, in the second position, the communication between the piston side chamber and the rod side chamber via at least a portion of the piston side conduit and at least a portion of the rod side conduit . - a hydraulic cylinder comprising a cylinder housing with first and second longitudinal ends, a piston in the cylinder housing, and a piston rod fixed to the piston and protruding through the first end of the cylinder housing, - an attachment element being connected to a protruding portion of the piston rod, and adapted to engage with a complementary element of the implement, and - a hydraulic conduit and valve arrangement (1201-1204), connected to the hydraulic cylinder , - characterized in that the conduit and valve arrangement (1201-1204) is arranged to selectively allow a communication between a piston side chamber of the hydraulic cylinder and a rod side chamber of the hydraulic cylinder , - a control valve , - a conduit arrangement , arranged to provide a communication between the hydraulic cylinder and the control valve , and - a locking valve arranged to allow, in a first position, the communication between the hydraulic cylinder and the control valve by means of the conduit arrangement , and to allow, in a second position, the communication between the piston side chamber and the rod side chamber of the hydraulic cylinder by means of the conduit arrangement , <EOS>