A fitting device for fitting a first fitting member held in a hand mounted at the forward end of a
robot arm to a corresponding second fitting member, comprising a detection unit for detecting the force or moment generated when the first and second fitting members come into contact with each other, and a judging unit for judging, based on the force or moment detected by the detection unit, whether a one-
point contact state prevails in which the first and second fitting members are in contact with each other at one point or a two-
point contact state prevails in which the first and second fitting members are in contact with each other at least two points. In the one-
point contact state, the first fitting member held in the hand is pressed against the second fitting member in the fitting direction thereby to proceed with the fitting operation while maintaining the holding posture of the
robot arm. In the two-point contact state, the fitting operation is caused to proceed further while the holding posture of the
robot arm is changeable. As a result, the first fitting member can be fitted in the second fitting member while keeping the robot arm in the normal posture.