In origin adjustment between two members which rotate relatively at a joint of an industrial robot, an origin adjustment apparatus is provided which is inexpensive and highly accurate and which requires extremely few man hours. In addition, an origin adjustment apparatus is provided which is so small in size as to be easily used even on a distal end shaft of a wrist of the robot and which requires no special signal line for origin adjustment. A mount member 23 where a positioning member 22 is embedded and a guide portion 24 along which the positioning member 22 slides in such a manner as to protrude are provided on either one or both of the two members which rotate relatively.