It is an object of the present invention to provide a driving force-transmitting device inexpensively. A driving force-transmitting device 10 comprises a housing 11 and 12, an inner shaft 18, a main clutch 22, a pilot clutch 24 and a cam mechanism 23 including a first and second cam members 26 and 25. Plural main outer and inner clutch disks 20 and 21 of the main clutch 22 are respectively spline-engaged with the housing 11 and the inner shaft 18. Plural pilot outer and inner clutch disks 32 and 33 of the pilot clutch 24 are respectively spline-engaged with the housing 11 and the first cam member 26 of the cam mechanism 23. The second cam member 25 of the cam mechanism 23 is arranged to constantly contact one of the main inner clutch disks 21 and is not spline-engaged with spline grooves of the inner shaft 18.