The invention provides a picking and placing device and an application method thereof. The picking and placing device comprises a conveyor belt, a bearing part, a plain scanning part, a manipulator, a first sensing device and a controller, wherein the first sensing device is used for sensing the position of an object outsides the bearing part and a vacancy on the bearing part; and the controller controls the manipulator to pick up the object outsides the bearing part and put the object into the vacancy of the bearing part according to a sensing result of the first sensing device. Thus, the picking and placing device can pick up and place the object by only needing one conveyor belt and one manipulator; reduces the occupying area and lowers the cost compared with the traditional picking and placing device with needing at least two conveyor belts; and in addition, can accurately fill the vacancy and improves the working efficiency by only adopting one manipulator without accurately calculating the picking and placing times.