of pulses thereby generating no overflow signal at a state where focusing lens element 5 has reached its closest focusing position and is prevented by a stopper mechanism in the lens barrel from moving further to a closer focusing position against the tendency of motor 12 to drive focusing lens element beyond the stopped position or where focusing lens element has reached its infinity focusing position to be prevented by a prevention mechanism from moving further beyond the stopped position in the direction of increasing the distance to be focused but the motor tends to displace the focusing lens element in the focused distance increasing direction gear 36 in gear mechanism 14 is forcedly stopped so that encoder 16 generates no pulse in such a case counter 17 being not reset counts the number of pulses from system controller 9 up to the full number n and generates an overflow pulse as is apparent from the above description the overflow pulse represents the drive impossible condition of the focusing lens element motor controller 10 in response to the overflow signal applied thereto generates such a control signal as to interrupt the power supply to motor 12 system controller 9 is actuated by the closure of manually operated automatic focusing initiation switch af sw and generates timing signals required for the sequential.