the rotor magnet is driven at a feed angle which is one half of the feed angle of the two phase driving in other words the feed angle of the one two phase driving is 9 degrees as shown in fig2 b an energizing process is performed in such a manner that energizing positions 1 u2032 2 u2032 3 u2032 and 4 u2032 3 u2032 and 4 u2032 being not shown in which one of the two coils is not energized are inserted between the energizing positions 1 2 3 and 4 of the two phase driving although it is not shown in fig2 b the energizing position 3 u2032 is obtained by not energizing the coil on the left side of the energizing position 3 shown in fig2 a also the energizing position 4 u2032 is obtained by not energizing the coil on the right side of the energizing position 4 shown in fig2 a in the case of the one two phase driving as shown in fig2 b the coils are energized in a cycle to obtain the above stated positions in the sequence of 1 u2192 1 u2032 u2192 2 u2192 2 u2032 u2192 3 u2192 3 u2032 u2192 4 u2192 4 u2032 in that order according to the energizing process the magnet rotor rotates counterclockwise as viewed in fig2 b if the energizing sequence is reversed the magnet rotor comes to rotate clockwise now it is assumed that the permanent magnet 110 of the stepping motor for driving the focusing lens group holder 108 in the optical axis direction is composed of the magnet rotor which.