PURPOSE: To shorten the access time and easily reduce the size of apparatus and realize thinner apparatus.

CONSTITUTION: A photo-interrupter 40 having the maximal value in the wider range than the RF signal is provided in the manner as movable like an objective lens 3a and a comparator 39 which can obtain a gate signal GATE indicating the wider positonal range of the objective lens including the positional range of the objective lens indicated by the FOK signal based on the light beam amount signal LS which is an output of the photointerrupter 40 is also provided. The optical pickup and focus servo apparatus is constituted so that the focus setup control is carried out in the section where the logical OR of the FOK signal and gate signal GATE can be obtained in the system controller 11.