A joint mechanism that can be used in an articulated finger unit of a robot hand has two actuators that are disposed in parallel with a vertical direction on a rear side of a perpendicular joint axle, and first and second drive bevel gears are coaxially connected and fixed to distal ends of output axles thereof. First and second driven bevel gears are fixedly mounted in coaxial manner on the perpendicular joint axle, and they mesh with the first and second drive bevel gears. The perpendicular joint axle is rotatably driven by the two actuators, and a revolving bracket connected thereto revolves to the left and right. The drive torque of the joint axle can be increased without increasing the horizontal dimensions of the joint axle.