To solve the problem with a conventional brake device for a working vehicle which has front drive hydraulic clutches provided with energizing members for thrusting a friction disc whereby the clutches are turned on to transmit the braking force of a rear wheel parking brake mechanism to front wheels, that it has a complicated construction and requires high cost.

This parking brake device for a four-wheel drive working vehicle has front drive hydraulic clutches 73, 74 provided on a front drive output shaft 30 for transmitting the power of a rear-wheel transmission system to front wheels 1 in a disconnectable manner. A lock mechanism 90 is provided on the front drive output shaft 30 or a front-wheel transmission shaft 14 and the lock mechanism 90 is connected in linkage with a parking brake lever 12.