To provide a transfer case which can be stopped by engagement so that direct front wheel drive is available and can be set free so that four wheel drive is available.

In front wheel drive, output of a central differential gear 140 is stopped by engagement with clutch collars 100, 220 and driving torque is transmitted only to a main driving line. In, four wheel drive, the clutch collars 100, 220 set the central differential gear 140 free from engagement to transmit the output from a sun gear 72 to a chain sprocket 250 in a secondary driving line. The central differential gear 140 is driven via a carrier and works as an open-type differential gear. A ring (external) gear 80 drives the main driving line and the sun (central) gear drives the secondary driving line via the chain sprocket 250 and a chain which interlock each other. The chain driving sprocket 250 has a constant dimension to implement deceleration between the driving sprocket 250 and a driven sprocket 268.