To heighten the quality of a piston member of a volume change absorbing means while suppressing the manufacturing cost of the piston member in a drive connecting device for four-wheel drive.

A four-wheel drive-drive connecting device for transmitting driving force, corresponding to rotating speed difference generated between one member 1 rotated interlockingly with one of front and rear wheels and the other member 2 rotated interlockingly with the other of the front and rear wheels, from an input side member 1 to an output side member 2 through the medium of generated pressure of a hydraulic pump 3 interposed between both members 1, 2 is provided with a volume change absorbing means 4 for absorbing volume change caused by the temperature change of hydraulic fluid of the hydraulic pump 3, and a piston member 43 of the volume change absorbing means 4 is a die-cast product. The piston member 43 is therefore high in quality and relatively low in cost.