A manipulator operative in a master/slave operative mode, comprising: a master unit commanding an operation; a slave unit having a work unit; a detector detecting the orientation of the master unit and the orientation of the slave unit; and a control device controlling the slave unit in response to the command from the master unit, wherein the control device includes: a function of determining a non-mater/slave operative mode or a master/slave operative mode; a function of calculating a difference between the orientation of the master unit and the orientation of the slave unit; and a function of comparing the absolute value of the difference with a preset reference value; and depending upon the result of the comparison, determining a normal master/slave operative mode or a transitional master/slave operative mode, in the master/slave operative mode, the transitional master/slave operative mode is a transitional mode from the non-master/slave operative mode to the master/slave operative mode.