A compound objective lens, an optical head device, an optical information device, and an information processing device that can inhibit the occurrence of aberration even when a light beam source wavelength shifts from the designed value. A diffraction structure having a sawtooth or stepwise cross section is formed in the region (R10) and region (R20). The height of the sawtooth or stepwise cross section formed in the region (R10) provides a light beam, which has a predetermined wavelength, with a difference in optical path length of N times the predetermined wavelength, as compared with a case of propagation in air. The height of the sawtooth or stepwise cross section formed in the region (R20) provides the light beam, which has the predetermined wavelength, with a difference in optical path length of J times the predetermined wavelength, as compared with a case of propagation in air. At least one of the difference in height between both ends of a boundary band (RB) provided between the region (R10) and the region (R20), and the width of the boundary band (RB) provides the light beam, which has the predetermined wavelength, with a difference in optical path length of (N+J)/2 times (N and J are mutually different natural numbers) the predetermined wavelength, as compared with a case of transmission in air.