A controller includes a generation unit that generates three-dimensional information, a deletion unit that deletes information about at least part of the measurement points in the three-dimensional information, and a determination unit that determines a state where the robot grips a workpiece. The generation unit generates first three-dimensional information before the robot implements an operation of gripping a target workpiece. The generation unit generates second three-dimensional information after the robot has implemented an operation of lifting the target workpiece. The deletion unit generates third three-dimensional information in which information about measurement points in the second three-dimensional information is deleted from the first three-dimensional information. The determination unit determines whether or not the workpiece in the third three-dimensional information matches the target workpiece.