To provide a lens unit for an optical pickup device, which is simple and inexpensive while different kinds of optical disks can be used, and to provide the optical pickup device using the same.

Since a diffraction plate DP emits zero-order diffraction light and first-order diffraction light to an incident luminous flux having a wavelength 1, a first objective lens OBJ1 can focus the light on an information recording surface of a BD when zero-order diffraction light is made incident and can focus the light on an information recording surface of an HD when first-order diffraction light is made incident. Thereby, a single first light source is used and the BD and the HD can be compatibly used with a simple and inexpensive construction without using a movable mirror and the like.