A fitting device and a fitting method, by which the fitting process can be carried out without damaging workpieces, even when a sufficient moment cannot be detected by pressing the workpiece in the fitting direction. The device includes a fitting status judging part adapted to judge whether a second workpiece is in motion in a fitting direction relative to a first workpiece; a workpiece orientation searching part adapted to change a current orientation of the second workpiece when it is judged that the second workpiece is not in motion in the fitting direction, and search a proper orientation for the second workpiece based on a detected force or speed of the second workpiece in the fitting direction, during the change of the orientation; and a fitting motion commanding part adapted to command a robot which grips the second workpiece to continue the fitting operation, by using the searched proper orientation.