An optical pickup device comprises a light source to emit a light flux
having wavelength .lamda.; an objective lens including at least two
plastic lenses of a first plastic lens having positive refractive power
and a second plastic lens having positive refractive power, wherein the
first plastic lens and the second plastic lens are arranged in this order
from the light source side; and an actuator to drive the objective lens;
wherein the objective lens satisfies the following expression (1-1):
-0.0004<.DELTA.3SA/(NA.sup.4f(1-m))<0.0004 (1-1) where .DELTA.3SA
(.lamda.RMS) represents a rate of change of a third order spherical
aberration of the objective lens when the temperature of an entire body
of the objective lens uniformly changes, f (mm) represents the focal
length of the objective lens for the light flux having wavelength
.lamda., and m represents the magnification of the objective lens.