To provide an information pickup device and an optical disk device which are compatible with each other, simple in structure, and compact by enabling one pickup to record and reproduce optical disks having different thickness and suppressing the light quantity loss as much as possible.

The objective lens for recording and reproduction which has positive refracting power and converges light from a light source on an information recording surface through the transparent substrate of an optical information recording medium has at least one lens surface composed of ≥3 ring-shaped lens surfaces having their centers on the optical axis, adjacent ring-shaped lens surfaces among the ≥3 ring-shaped lens surfaces are different in refracting power, and the ring-shaped lens surface positioned at the outermost periphery has a refracting power corrsponding to the optical information recording medium having the thinnest transparent substrate among plural optical information recording media having transparent substrates differing in thickness, so that the light is converged on the information recording surfaces of the respective optical information recording media having the transparent substrates differing in thickness.