PROBLEM TO BE SOLVED: To achieve thin diameter of an insertion part, and perform high-precision lens position control in simple and compact constitution in an electronic endoscopic device in which the lens is driven by use of torque wire.SOLUTION: As power of the electronic endoscope is charged, it is rotated to the Tele side to a point P1 where the motor rotation speed is lower than the threshold value. Then it is rotated to the Wide side to a point P2 where motor rotation speed is lower than the threshold value. Motor rotation is counted in rotation from the point P1 to the point P2, and rotation quantity A1 to a rotatable range of the motor is detected. Defining that the center of a mechanically movable range A3 of a cam ring coincides with the center of the rotatable range of the motor, a usable range A2 for motor control in lens position control is determined based on the rotation number corresponding to the mechanically movable range A3 of the cam ring obtained from the design. A Wide side end point P3 of the usable range A2 is set for an origin in lens control processes, and the motor is moved to the point P3.
