The invention discloses an end effector device of an under-actuated picking manipulator. The end effector device comprises three fingers with the same structure, a transmission mechanism, three contacting plates, three connecting rods, a driving rod and a rotary disk, wherein each finger has three joints, and one end of the first joint of each finger is uniformly arranged on the rotary disk; and each finger is provided with one contacting plate. The working mechanism of the end effector is that the driving rod is driven by a motor to move and drives the three fingers to oppositely move to close by the connecting rods; when the contacting plates of the fingers contact fruits and vegetables, the fruits and vegetables can push the contacting plates to slide so as to drive the incomplete gear movement in the second joints of the fingers, and the meshed gears drive the third joints of the fingers to move; when force sensors on the surfaces of the contacting plates detect preset grasping force, signals are fed back to the motor, the driving rod is controlled to stop moving, and the motor drives the rotary disk to rotate, so that the picking of the fruits and vegetables is realized. The end effector device can be used for picking fruits and vegetables, and if the end effector device is used together with other device such as a robot, the high-efficiency and high-reliability picking operation is achieved.