A lens position detecting device 200 has a position detecting magnet 202, a magnetic force detecting sensor 204, a positional information generating means 206, etc. The position detecting magnet 202 is mounted on a rear surface of a lens holder frame 1460. The magnetic force detecting sensor 204 serves to generate a detected signal having a magnitude depending on the intensity of a magnetic force generated from the magnetic poles of the position detecting magnet 202. The magnetic force detecting sensor 204 is disposed on a straight line that passes through the position detecting magnet 202 parallel to the optical axis. The magnetic force detecting sensor 204 outputs a detected signal having a voltage corresponding (proportional) to the intensity of the magnetic force. An amplifying circuit 208 of a positional information generating means 206 amplifies the detected signal Ss from the magnetic force detecting sensor 204.