A connecting device for detachably coupling an attachment device to a working device, comprising: - a supporting device, which is fixed or can be fixed to the working device, and on which a first receptacle for a first coupling part of the attachment device and a second receptacle for a second coupling part of the attachment device are formed, wherein the receptacles (46, 70) are arranged at a distance from one another on the supporting device; - a locking device, which is held on the supporting device and comprises an actuator and a locking element, which can be transferred by the latter from a loosening position into a holding position and vice versa, wherein the first receptacle is released in the loosening position for the insertion of the first coupling part and the first coupling part is held in the first receptacle in the holding position; - a securing device comprising a securing element that is movably held on the supporting device, which securing element can be transferred from a release position to a securing position and vice versa, wherein an insertion opening of the second receptacle for the second coupling part is released in the release position and blocked in the securing position; and - a coupling device, via which the securing device is operatively connected to the locking device, wherein the securing element is transferred from the securing position to the release position when the locking element is transferred from the holding position to the loosening position, wherein the coupling device comprises an energy storage element, which is arranged between the locking element and the securing element in such a way that the energy storage element limits a force, which is applied to the securing element by the locking device, and which can be applied to the securing device in order to transfer the securing element from the securing position to the release position, characterized in that the securing element can be transferred from the securing position to the release position independently of the locking element assuming the loosening position or the holding position. - a supporting device, which is fixed or can be fixed to the working device, and on which a first receptacle for a first coupling part of the attachment device and a second receptacle for a second coupling part of the attachment device are formed, wherein the receptacles (46, 70) are arranged at a distance from one another on the supporting device; - a locking device, which is held on the supporting device and comprises an actuator and a locking element, which can be transferred by the latter from a loosening position into a holding position and vice versa, wherein the first receptacle is released in the loosening position for the insertion of the first coupling part and the first coupling part is held in the first receptacle in the holding position; - a securing device comprising a securing element that is movably held on the supporting device, which securing element can be transferred from a release position to a securing position and vice versa, wherein an insertion opening of the second receptacle for the second coupling part is released in the release position and blocked in the securing position; and - a coupling device, via which the securing device is operatively connected to the locking device, wherein the securing element is transferred from the securing position to the release position when the locking element is transferred from the holding position to the loosening position, the coupling device comprises an energy storage element, which is arranged between the locking element and the securing element in such a way that the energy storage element limits a force, which is applied to the securing element by the locking device, and which can be applied to the securing device in order to transfer the securing element from the securing position to the release position, characterized in that the securing element can be transferred from the securing position to the release position independently of the locking element assuming the loosening position or the holding position.